JP2003291030A - Electrode wire for wire electrical discharge machining - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure of electrode wire for wire electrical discharge machining for manufacturing wire with reduced manufacturing processes and greatly improved machining speed as compared with conventional electrode wire and providing roughness of a finished surface and dimension accuracy equivalent to those by conventional electrode wire, and a method for manufacturing the same. <P>SOLUTION: Electrode wire for electrical discharge machining 1 has a core material 2 composed of brass containing 68-82 wt.% of Cu and rest of Zn and a copper-zinc alloy multi layer structure having concentration gradient with increasing zinc concentration as it gets apart from the core material 2. An outermost layer contains 95% or more zinc concentration and has a thickness of 8-16% of total outer diameter. The method for manufacturing the electrode wire for electrical discharge machining 1 comprises a first process to apply zinc plating of a thickness of 10-50 μm on brass wire of 0.5-1.3 mm containing 68-82% wt.% of Cu and rest of Zn, a second process to perform heat treatment by passing through a heating furnace of 500-2,000 mm length generating 800-900°C oxidation atmosphere at 3.0-10 m/min speed, and a third process to extend the wire thereafter. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode wire used in a wire electric discharge machine, and more particularly to a wire electric discharge machine which can reduce the number of manufacturing processes and greatly improve the machining speed as compared with the conventional one. TECHNICAL FIELD The present invention relates to a structure of a manufacturing electrode wire and a manufacturing method thereof.

[0002]

2. Description of the Related Art Wire electric discharge machining is a process in which an electric discharge phenomenon is caused between an electrode wire for electric discharge machining and a work piece, and the work piece is cut by thermal energy generated by the electric discharge. Suitable for metal processing with complicated shapes such as molds. In such wire electric discharge machining, it is required that the finished state of the surface of the workpiece and the dimensional accuracy be good and that the machining time be short. The electrode wire that has been widely used conventionally is 65/35 brass (65% Cu-35% Zn). Various methods have been studied to increase the electric discharge machining speed compared to this structure. One of them is to increase the Zn concentration in the brass composition. (Journal of Copper and Copper Technology 26
(1987)) Further, as shown in FIGS. 2A and 2B, many proposals have been made on a composite structure in which an alloy layer having a higher Zn concentration is formed on the wire surface and a manufacturing method thereof. (Japanese Patent Publication No. 57-5648 and others)

[0003]

According to these various studies, the electric discharge machining speed varies depending on the comparison method.
When machining is performed so that the surface roughness of the obtained workpiece is the same, an electric discharge machining speed exceeding 1.5 times that of 65/35 brass is obtained. However, from the viewpoint of cost performance, further improvement in processing speed, cost reduction, and ease of wire production are desired. Further, in order to improve the machining speed, it is necessary that the roughness and dimensional accuracy of the machined surface finished by electric discharge machining are not inferior to those in the past. In addition, it is an industrially indispensable problem that the wire has few steps and has good productivity in manufacturing.

[0004]

In order to solve these problems, the present invention has made extensive studies and as a result, firstly Cu 68 to 8
As the central core material 2 made of brass with 2 wt% and the balance Zn is separated from the central core material 2, a multilayer structure of a copper-zinc alloy is formed in which the zinc concentration is increased to have a concentration gradient, and the zinc concentration of the outermost layer is 95% or more and 8 of the total outer diameter
In the electric discharge machining electrode wire 1 having a thickness of ˜16%, secondly, Cu of 68 to 82 wt% and the balance of 0.5 to 1.
The first step of galvanizing 3 mm brass to a thickness of 10 to 50 μm, and a heating furnace having a furnace length of 500 to 2,000 mm in an oxidizing atmosphere at 800 to 900 ° C. and a speed of 3.0 to 10 m.
It is a method for manufacturing the electrode wire 1 for electric discharge machining, which includes a second step of performing heat treatment by passing the electrode wire at a speed of / min and a third step of drawing the wire.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. First, as an introduction, the following is the result of a compilation of experiments conducted by us regarding what kind of structure is optimal for improving the electric discharge machining speed of a wire. The central layer of the wire has high conductivity,
High-strength metal between ℃ is good. The central layer of is a part that is not consumed by discharge, and Zn for improving so-called discharge characteristics is not necessarily required. However, Cu
Although a high conductivity can be obtained when used alone, a brass alloy such as 80/20 or 70/30 brass is suitable because the tensile strength of the wire becomes small. In the case of a single-structure wire having no composite structure, the higher the Zn concentration is, the faster the processing speed can be obtained. With the composite structure as described above, the conductivity is 70/30 which is higher than that of 65/35 brass. It has been found that brass and 80/20 brass have a higher electric discharge machining rate. Around the central metal, a copper alloy capable of cold drawing and having a zinc concentration as high as possible (Zn concentration 40-50 wt%) is preferably coated to a thickness of about 10% of the outer diameter, at least 7% or more. With respect to the alloy layer having a high zinc concentration, the portion where the wire is consumed by electric discharge machining is about 10% from the surface layer with respect to the outer diameter, and therefore the zinc concentration may be increased only in this portion. However, according to the experiment, the outer diameter of 10
% Metal of Zn100% has no effect, and Cu-Zn alloy is good for coating. This layer is a very important part for improving the electric discharge machining speed, and when the thickness is less than 7% of the outer diameter, the performance is not improved. 7%
In the above case, the performance of the electric discharge machining speed is remarkably improved, but even if the thickness is set to 10% or more, the effect is not further improved. Rather, the β concentration of brass is high and the zinc concentration is 40-
50% is a composition in which wire drawing is difficult, and if there is no effect of improving the electric discharge machining speed, it is preferably as thin as possible, and 7-12% is suitable. The outermost layer is preferably coated with Zn in a thickness of 1-15% of the outer diameter. For galvanizing, the outer diameter is 0.3
It covers a quantity of -15%, but by adding this, a catalytic function for exciting the discharge phenomenon can be obtained. If the thickness of the galvanization is thicker than this, it adversely affects the dimensional accuracy, the deposit on the work piece, and the automatic connection property of the electric discharge machine.

Example 1 First, an example in which the electrical discharge machining characteristics of brass alloys alone were compared will be described. Wire outer diameter 0.3 mm, work material SKD-11, work thickness 60 mm, machining is performed under rough machining conditions using electric discharge machine SX10, and if wire breakage does not occur after 10 minutes of machining, IP (machining setting) Was increased by 1 notch and the maximum electric discharge machining speed of each wire was obtained. The results are shown in Table 1.

[0006]

[Table 1]

From these results, it can be confirmed that 65/35 brass has the highest processing speed. This supports that it is said that the higher the Zn concentration is, the better the speed of the electric discharge machining is.

[Example 2] Next, as Example 2, the central metal of Example 1 was coated with brass having a high zinc concentration and the characteristics were evaluated in the same manner. In order to form brass with high zinc concentration in the central metal,
Zinc plating on the surface of various brass wire 0.9φ 850 ℃
It was heated in an oxidizing atmosphere and coated with brass having a high zinc concentration by thermal diffusion. This is drawn to 0.3φ and annealed,
It was used as a test sample. The results of evaluation of the maximum processing speed under the same conditions as in Example 1 are shown in Table 2.

[0008]

[Table 2]

As can be seen from the results shown in Table 2, by forming the high zinc layer, the electric discharge machining speed is significantly improved and the tendency of the machining speed is opposite to that of the first embodiment, and is 65/3.
80/2 is the slowest when 5 is used as the central metal
The interesting result was that using 0 was the fastest.

Example 3 Further, as Example 3, a wire having the structure of Example 2 and having the outermost layer zinc-plated was evaluated.
After forming the wire of the structure of Example 2 with 0.9φ, Zn was formed on this surface by electroplating. This was drawn to 0.3φ and annealed to obtain a test sample. Examples 1 and 2
Table 3 shows the results of evaluation of the maximum processing speed under the same conditions as above.
Shown in.

[0010]

[Table 3]

From the results shown in Table 3, it was revealed that the galvanizing of the outermost layer of the wire similarly increases the processing speed for any composition. It can be seen that a zinc plating thickness of 5 μm is sufficiently effective. Therefore, since the thickness of the wire is 0.3 μm and the thickness is 5 μm, the working speed can be improved if the outer diameter of the wire is about 1.7% of zinc plating.

[Fourth Embodiment] Finally, in the manufacturing method of the fourth embodiment, the zinc plating is applied after the thermal diffusion. However, by selecting the heat treatment conditions, the heat treatment is performed without forming the zinc plating in the outermost layer in another step. It turned out that it can be formed by. 80
/ 20 brass 0.775 mm with zinc plating 30 μm thick
Was heat-treated by passing it through a heating furnace having a furnace length of 1,000 mm at a speed of 6.0 m / min in an oxidizing atmosphere, and then wire drawing to obtain a wire of 0.3 mm. 70/3 when 70/30 is used as the central metal
0 Brass 0.775 mm is coated with zinc plating to a thickness of 30 μm, and heat treatment is performed by passing it through a heating furnace with a furnace length of 1,000 mm in an oxidizing atmosphere at a speed of 6.0 m / min, and then drawing wire 0 A wire of 0.3 mm was obtained. The processing speed of this wire was 258.8 mm ² / min, the tensile strength was 802.6 MPa, and the elongation was 1.60%. When the concentration distribution of the cross section of this wire was examined by EPMA (Electron Probe Microanalyzer), the results shown in Table 4 below were shown.

[0012]

[Table 4]

From these results, it can be seen that the concentration gradient is such that the zinc concentration becomes lower toward the center when the surface layer has a zinc concentration of 100%. In the case where this structure is the case of Example 3, in comparison with the structure in which the surface layer is zinc-plated after being diffused by heat treatment, the structure in Example 4 is the structure intended in one step of heat treatment. It can be seen that this is an industrially valuable manufacturing method in which

Up to now, a copper-zinc alloy has been described as a typical example of the copper alloy, but the copper alloy is not limited to this, and copper-tin, copper-magnesium, copper-silver, copper-chromium alloy, etc. may be used. It goes without saying that it is within the scope of the present invention.

[0015]

As described above, according to the present invention, not only the number of manufacturing steps can be reduced and the electric discharge machining speed can be greatly improved, but also excellent effects can be exhibited in the automatic wire connection. Its industrial value is extremely high.

[Brief description of drawings]

FIG. 1 (a) is a manufacturing process diagram of an electrode wire 1 for wire electric discharge machining of the present invention. (B) It is a structural cross-sectional view of an electrode wire 1 for wire electric discharge machining of the present invention.

FIG. 2A is a manufacturing process diagram of a conventional wire electric discharge machining electrode wire 1 '. (B) It is a structural cross-sectional view of a conventional wire electric discharge machining electrode wire 1 '.

[Explanation of symbols]

1 Electrode Wire for Wire Electric Discharge Machining of the Present Invention 2 Core material (Cu 68 to 82 wt%, brass with Zn balance) 3A Copper-zinc alloy layer 3B Copper-zinc alloy layer 3C Copper-zinc alloy layer 3D Copper-zinc alloy layer 3E Copper -Zinc alloy layer (outermost layer) (Zinc concentration: 95%
8 to 16% of the total outer diameter) 1'Conventional wire electric discharge machining electrode wire 2'Central core material (copper alloy) 3'Copper-zinc alloy layer 4'Zinc plating layer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masakazu Yoshimoto             2-12 Shimoodachu, Nakahara-ku, Kawasaki-shi, Kanagawa             No. 8 Oki Electric Cable Co., Ltd. (72) Inventor Yoichiro Kimoto             2-12 Shimoodachu, Nakahara-ku, Kawasaki-shi, Kanagawa             No. 8 Oki Electric Cable Co., Ltd. F-term (reference) 3C059 AA01 AB05 DC01

Claims (2)

[Claims] 1. A multilayer structure of a copper-zinc alloy in which a zinc concentration is increased and a concentration gradient is given to a central core material 2 made of brass with 68 to 82 wt% Cu and the balance Zn, as the distance from the central core material 2 increases, The electrode wire 1 for electric discharge machining, wherein the outermost layer has a zinc concentration of 95% or more and a thickness of 8 to 16% of the total outer diameter. 2. A first step of zinc-plating brass having a thickness of 10 to 50 μm on brass of 0.5 to 1.3 mm consisting of 68 to 82 wt% Cu and the balance Zn, and a furnace length of 500 to 2,000 m.
m heating furnace in 800 to 900 ° C. in an oxidizing atmosphere at a rate of 3.0 to 10 m / min for heat treatment, and then a third step of wire drawing. A method for manufacturing an electrode wire 1 for electric discharge machining.