JP2002137123A - Electrode wire for wire electric discharge machining - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode wire for wire electric discharge machining capable of realizing a higher speed than a conventional electrode wire to reduce machining cost. SOLUTION: In this electrode wire for wire electric discharge machining in which a core member is made of copper zinc alloy containing zinc of 15 to 30 wt.%, an outer layer 3 is formed with a thickness of 6% or more of a finish outside diameter of high zinc brass having zinc concentration of 48 to 68 wt.% on a surface of the core member, and a zinc covered layer is provided with a thickness of 0.5 to 2% of a total finish outside diameter as an outermost layer 4 at its outer periphery furthermore, it is possible to realize a higher machining speed at which a workpiece is cut by 20% or more than the conventional wire when, in particular, a dielectric constant of the electrode wire calculated according to an calculation expression of electrode wire dielectric constant becomes 23% or more, preferably, it becomes 29% or more in the case of copper alloy when the core member contains zinc of 15 wt.%, and it becomes 27% or more in the case of copper alloy when the core member contains zinc of 20 wt.%, and it becomes 24% or more in the case of copper alloy when the core member contains zinc of 30 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode wire for wire electric discharge machining, and in particular, to increase the machining speed for cutting a cutting object in order to keep machining costs low, and to achieve a higher speed than a conventional wire. The present invention relates to an electrode wire for wire electric discharge machining capable of performing the following.

[0002]

2. Description of the Related Art Wire electric discharge machining is a machining method in which a discharge phenomenon is caused between an electrode wire for wire electric discharge machining and a cut object, and the cut object is machined into a thread saw. It is a suitable processing method. For such an electrode wire for wire electric discharge machining, an inexpensive electrode wire capable of high-speed machining so as to reduce machining cost has been desired. Further, from the viewpoint of ease of use, there has been a demand for a wire capable of automatic connection and an electrode wire free from occurrence of disconnection of the electrode wire, which can cope with unmanned processing. Conventional electric discharge machining electrode wire 1 ′
As shown in FIG. 2 (a), even if sufficient characteristics cannot be obtained, zinc is 35 to 40% by weight because of its cost merit.
The electrode wire 1 'for wire electric discharge machining having a single-layer structure of a copper-zinc alloy core material 2' containing iron has become mainstream and has been widely and generally used. However, the electrode wire 1 'made of a copper-zinc alloy containing 35 to 40% by weight of zinc is satisfactory in cost because of a single-layer structure, but has a slight increase in the processing speed for shaving a cut object. There were difficulties. In general, it is said that the higher the zinc content, the faster the processing speed for shaving a cut object. However, if the zinc concentration exceeds 40%, the wire drawing workability becomes extremely poor, and the wire drawing becomes difficult. Some proposals for solving this drawability have been submitted, but they have not been put to practical use yet. 2. Description of the Related Art In recent years, as a wire capable of high-speed machining, a two-layer wire electric discharge electrode having a core material 2 ″ and an outer layer 3 ″ made of high zinc brass as shown in FIG. Line 1 "has been proposed.

[0003]

The electrode wire 1 "having such a two-layer structure is a single-structure electrode wire (35 to 40% by weight of zinc).
The processing speed for shaving the cuttings is higher than that of the containing copper-zinc alloy electrode wire), but users have demanded the emergence of electrode wires with higher cutting speeds for shaving the cuttings. I have.

[0004]

In order to solve these problems, the present invention has made intensive studies. As a result, a high zinc brass layer on a core material is formed by subjecting a core material made of a copper alloy to galvanization,
This can be formed by heat treatment.
The composition and thickness of this high zinc brass layer depends on the composition and outer diameter of the core material,
The present inventors have found that, depending on the thickness of the zinc plating and the conditions of the heat treatment, there is a region where the conductivity is particularly high by appropriately selecting these. Furthermore, it was also found that a material having a high conductivity has a high machining speed for cutting a cutting object in wire electric discharge machining. The present invention
The core material is a copper-zinc alloy containing 15 to 30 wt% zinc,
On the surface of the core material, high zinc brass having a zinc concentration of 48 to 68 wt% is formed as an outer layer 3 with a thickness of 6% or more of the finished outer diameter. In the electrode wire for wire electric discharge machining provided with a thickness of 0.5 to 2%, particularly, the conductivity of the electrode wire calculated by the formula for calculating the electrode wire conductivity is 23% or more. 29 for copper alloy containing 15 wt% zinc
% Or more, if the core material is copper alloy containing 20 wt% zinc, it is 27% or more, and if the core material is copper alloy containing 30 wt% zinc, it is 24% or more. This is an electrode wire for wire electric discharge machining that can achieve a speed increase of 20% or more than that of the above-mentioned wire.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the electrode wire 1 for wire electric discharge machining according to the present invention will be described below in detail with reference to the attached documents. FIG. 1A is a sectional view of an electrode wire 1 for wire electric discharge machining according to the present invention. As is clear from the figure, the core 2 is provided at the center, the outer layer 3 is provided around the core 2, and the outermost layer 4 is provided therearound. The electrode wire 1 for wire electric discharge machining according to the present invention has a core 2 made of a copper-zinc alloy containing 15 to 30% by weight of zinc, and a high zinc brass having a zinc concentration of 48 to 68% by weight as an outer layer 3 on the surface of the core. And a zinc coating layer provided on the outer periphery thereof as an outermost layer 8 with a thickness of 0.5 to 2% of the total finished outer diameter. An electrode wire for wire electric discharge machining, wherein the conductivity of the electrode wire calculated by the following formula 1 for calculating the electrode wire conductivity is 23% or more.

[0006]

(Equation 1)

[0007] The thickness of the outer layer 3 which contributes to an increase in the electric discharge machining speed for cutting a cut object is set to 6% or more of the finished outer diameter. If the thickness is less than 6%, the high zinc brass layer is consumed by electric discharge. This is because, since the thickness is smaller than the thickness, the processing speed for shaving the cut object is reduced as a result. The reason why the thickness of the outermost layer 4 is set to 0.5 to 2% of the total finished outer diameter is 0.5%.
If it is less than the above, there is not much effect of providing the outermost layer, and if it is more than 2%, a large amount of sludge is generated at the time of electric discharge machining, causing various adverse effects.

[0008]

EXAMPLE 1 A zinc coating layer having a thickness of 25 μm was provided on the outer layer of a copper-zinc alloy wire having a diameter of 0.78 mm containing 20 wt% of zinc, and then the wire was run in an atmosphere at 850 ° C. for a certain period of time. Heat treated to produce high zinc brass layer. Further, zinc plating is applied to the wire surface as an outermost layer at a thickness of 9 μm. Finally, cold drawing was performed using this wire as a bus bar to produce an electrode wire for wire electric discharge machining having an outer diameter of 0.3 mm. The conductivity of the thus obtained electrode wires for wire electric discharge machining having different heat treatment times was measured. The electrode wire was set in a wire electric discharge machine, processed under the conditions shown in Table 1 below, and the processing speed at which a cut object was cut was measured. Separately, the processing speed for shaving a conventional electrode wire obtained by drawing a copper-zinc alloy containing 35 wt% of zinc to φ0.3 mm was also measured.

[0009]

[Table 1]

[0010]

EXAMPLE 2 A zinc coating layer having a thickness of 17 μm was provided on the outer layer of a copper-zinc alloy wire having a diameter of 0.78 mm containing 30% by weight of zinc, and then the wire was run in an atmosphere at 850 ° C. for a certain period of time. Heat treated to produce high zinc brass layer. Further, zinc plating is applied to the wire surface as an outermost layer at a thickness of 9 μm. Finally, cold drawing was performed using this wire as a bus bar to produce an electrode wire for wire electric discharge machining having an outer diameter of 0.3 mm. The electrical conductivity of the electrode wire thus obtained and the processing speed for shaving the cut object were measured in the same manner as in Example 1.

[0011]

Example 3 A zinc coating layer having a thickness of 35 μm was provided on the outer layer of a copper-zinc alloy wire of φ0.9 mm containing 15 wt% of zinc, and then the wire was run in an atmosphere at 850 ° C. for a certain period of time. Heat treated to produce high zinc brass layer. Further, the surface of the wire is plated with a zinc plating having a thickness of 10 μm as an outermost layer. Finally, cold drawing was performed using this wire as a bus bar to produce an electrode wire for wire electric discharge machining having an outer diameter of 0.3 mm. The electrical conductivity of the electrode wire thus obtained and the processing speed for shaving the cut object were measured in the same manner as in Example 1. 1 (b) to 1 (d) show Examples 1 to 4.
3 is a graph showing the relationship between the heat treatment time and the electrical conductivity of the electrode wire of No. 3 and the relationship between the heat treatment time and the processing speed for shaving a cut object. The processing speed ratio in the graph refers to a conventional copper-zinc alloy containing 35 wt% of zinc, which is φ0.
This is the speed ratio with the electrode wire obtained by wire drawing up to 3 mm. The larger the value, the faster the working speed. As is clear from FIGS. 1 (b) to 1 (d), the conductivity of the obtained electrode wire increases as the heat treatment time increases, and reaches a maximum value during a certain heat treatment time. Further, if the heat treatment time is further increased, the conductivity will decrease with the heat treatment time. Also, the processing speed is synchronized with the conductivity, and it increases with the heat treatment time,
The maximum value is reached under certain heat treatment conditions, and when the heat treatment time is prolonged, the speed decreases.

[0012]

Example 4 The same pre-heat treatment wire as in Example 1 except that a zinc coating layer having a thickness of 25 μm was provided on the outer layer of a copper-zinc alloy wire having a diameter of 0.78 mm containing 20 wt% of zinc and having the maximum conductivity in Example 1 And a high zinc brass layer was formed under heat treatment conditions (at 850 ° C. in an atmosphere for 17 seconds). Cold drawing is performed using this wire as a bus bar, and the outer diameter is φ0.3 mm.
The production of the electrode wire for wire electric discharge machining was attempted, but the wire was broken during the wire drawing. As a result of observing the disconnection point, it was found that a crack generated on the surface of the wire was a starting point and the wire was disconnected. In addition, as a result of observing the wire surface in a portion where the wire could be drawn without disconnection, it was observed that countless cracks were generated on the electrode wire surface. As a result of analyzing the high zinc brass layer of the electrode wire manufactured under the heat treatment condition in which the conductivity of Examples 1 to 3 reached the maximum value and the electrode wire of Example 4 by EPMA (electron beam microanalyzer), zinc 48 was obtained. ~ 68w
It was found to be a copper-zinc alloy containing t%. The region indicated by 48 to 68 wt% of zinc is a mixed crystal region of β + γ or a γ phase region in the phase diagram of the copper-zinc alloy, and this phase is a phase in which wire drawing is difficult. The cracks of Example 4 were such that these phases could not be fully expanded during wire drawing and appeared on the surface in the form of cracks. In contrast, Examples 1 to
Despite the fact that the composition of the high zinc brass layer of No. 3 is also a β + γ mixed crystal region or a γ phase region, no cracks are observed on the wire surface because the zinc coating layer exists outside this phase to perform wire drawing. It is possible. In other words, even if a phase in the β + γ mixed crystal region or γ region where wire drawing is difficult at this level of workability is outside the core material, the layer that can be drawn further outside is a β + γ mixed crystal phase. Alternatively, it is because the wire drawing process can be performed by supplementing the wire drawing processability of the γ phase.

Conventionally commercialized, zinc 2
An electrode wire made of a copper-zinc alloy containing 0% and provided with a high zinc brass layer as an outer layer has a conductivity of 26% in order to avoid a β + γ mixed crystal region or a γ phase region in which wire drawing is difficult. %
It was about.

Until now, the core material has been described as a copper-zinc alloy containing 15 to 30 wt% of zinc, but other modifications may be used. In addition, although the outermost layer has been described with reference to the zinc coating layer, copper or other metal capable of wire drawing may be used. As described above, depending on the heat treatment conditions, there are conditions under which the electrical conductivity is maximized, and in that part, the electrode wire for wire electric discharge machining utilizing the effect that the processing speed for processing the cut object also shows the maximum value is within the scope of the present invention. It goes without saying that

Due to the above structure, the electrode wire 1 for wire electric discharge machining of the present invention showed better results than existing products as a result of a reliability test and a continuity test.

[0016]

As described above, according to the electrode wire 1 for wire electric discharge machining of the present invention, in order to keep machining costs low, the machining speed for shaving a cut material is 20% or more higher than that of a conventional wire. It is an electrode wire for wire electric discharge machining that can be measured, and its industrial value is very large.

[Brief description of the drawings]

FIG. 1A is an electrode wire 1 for wire electric discharge machining according to the present invention.
FIG. (B) is a diagram showing the relationship between the electrical conductivity and the machining speed ratio with respect to a conventional product with respect to the heat treatment time of the electrode wire in the first embodiment of the electrode wire for wire electric discharge machining 1 of the present invention. (C) is a view showing the relationship between the conductivity with respect to the heat treatment time of the electrode wire and the machining speed ratio with the conventional product in the second embodiment of the electrode wire 1 for wire electric discharge machining of the present invention. (D)
It is a figure which shows the relationship between the electric conductivity with respect to the heat processing time of an electrode wire, and the machining speed ratio with the conventional product in 3rd Example of the electrode wire 1 for wire electric discharge machining of the present invention.

FIG. 2A shows a conventional electrode wire 1 ′ for wire electric discharge machining.
FIG. 4 is a cross-sectional view of a first embodiment of the present invention, which has a single-layer structure of a core material 2 ′ made of a copper-zinc alloy containing 35 to 40 wt% of zinc. (B) is a cross-sectional view of a second embodiment of the conventional electrode wire 1 "for wire electric discharge machining, having a two-layer structure of a core 2" and an outer layer 3 ".

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Electrode wire for wire electric discharge machining of the present invention 2 Core material 3 Outer layer 4 Outermost layer 1 'Electrode wire for conventional wire electric discharge machining 2' Core material made of copper-zinc alloy having 35 to 40 wt% of zinc 1 "Conventional wire electric discharge machining Electrode wire 2 "core material 3" outer layer

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoichiro Kimoto 2-12-8 Shimoodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside the Oki Electric Cable Co., Ltd. (72) Inventor Kazuki Hayasaka 2 Shimoodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Chome 12-8 Oki Electric Cable Co., Ltd. F term (reference) 3C059 AA01 AB05 DB03 DC02

Claims (4)

[Claims] 1. A core material made of a copper-zinc alloy containing 15 to 30% by weight of zinc, and high zinc brass having a zinc concentration of 48 to 68% by weight formed on the surface of the core material to a thickness of 6% or more of the finished outer diameter. Further, an electrode wire for wire electric discharge machining, wherein a zinc coating layer is provided on the outer periphery with a thickness of 0.5 to 2% of a total finished outer diameter and has a conductivity of 23% or more. 2. A copper-zinc alloy containing 15% by weight of zinc is used as a core material, and high zinc brass having a zinc concentration of 48 to 68% by weight is formed on the surface of the core material at a thickness of 6% or more of the finished outer diameter. Zinc coating layer on the outer circumference
An electrode wire for wire electric discharge machining, which is provided with a thickness of 5 to 2% and has a conductivity of 29% or more. 3. A core material made of a copper-zinc alloy containing 20% by weight of zinc, and high zinc brass having a zinc concentration of 48 to 68% by weight is formed on the surface of the core material to a thickness of 6% or more of the finished outer diameter. With a zinc coating layer of 0.5
An electrode wire for wire electric discharge machining, wherein the electrode wire has a thickness of about 2% and a conductivity of 27% or more. 4. A copper-zinc alloy containing 30% by weight of zinc is used as a core material, and high zinc brass having a zinc concentration of 48 to 68% by weight is formed on the surface of the core material to a thickness of 6% or more of the finished outer diameter. Zinc coating layer on the outer circumference
An electrode wire for wire electric discharge machining, which is provided with a thickness of 5 to 2% and has a conductivity of 24% or more.