JP2003311544A - Electrode wire for wire electric discharge machining - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric wire designed to suppress the increase in the number of vibrations during electric discharge machining which is an inhibiting factor for stability of electric discharge machining and also designed to eliminate disconnection and improve electric discharge machining performance. <P>SOLUTION: An electrode wire 1 comprises a core material 2 made of a copper line and a plating layer which is formed around the face of the core material 2 and composed of double layers of a lower layer 3 of brass plating and an upper layer 4 of zinc plating. The line diameter d of the electrode wire 1 is 0.02-0.20 mm and tensile strength Ts is (-2500d+3000) to (-2500d+4500) MPa. <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 as a tool electrode for wire electric discharge machining, which is particularly suitable for minute and high-precision machining of parts constituting precision equipment (hereinafter referred to as "workpiece"). Regarding the line.

[0002]

2. Description of the Related Art Wire electric discharge machining uses a thin wire as an electrode wire to supply a machining liquid (highly pure water) to an electric discharge site.
Applying a voltage to the electrode wire and the work piece (mold, die, etc.) and continuously running with tension applied to the electrode wire, while repeating pulsed discharge in the working fluid between the work piece and the electrode wire. It is generated and the workpiece is processed by this discharge energy. The electric discharge consists of the steps of melting, explosion, scattering, cooling, and sludge removal.When the electrode wire and the work piece approach each other continuously, the above electric discharge machining is repeatedly executed, and the work piece It is processed into the shape of.

In recent years, precision equipment tends to be compact, and there is an increasing need for further miniaturization and refinement of the size and shape of the work piece. Along with this, it is required to further improve the electric discharge machining accuracy (surface roughness and dimensional accuracy).

In order to process a work piece having a very small size and shape, it is necessary to make the wire diameter of the electrode wire as small as possible.
Further, since the vibration generated by the explosion during electric discharge machining has a great influence on the accuracy of electric discharge machining, it is necessary to apply a high tension to the electrode wire. Therefore, in the case of electric discharge machining of a minute work piece having a high working accuracy, a thinner electrode wire having a high tensile strength is required.

Conventionally, as an electrode wire for fine / precision machining,
Heavy metal wires such as tungsten and molybdenum are generally used. These heavy metal wires have tensile strength capable of withstanding the tension applied during processing. However, there are problems that the material itself is expensive, the wire drawing process is difficult, the processing cost for miniaturization is high, and the electric discharge machining performance is inferior to that of the brass wire.

Then, as an electrode wire replacing the heavy metal wire,
Various proposals have been made for a steel wire as the core material (Japanese Patent Application Laid-Open No. 20-1999)
No. 00-107943, Japanese Patent Laid-Open No. 2000-19802.
No. 7, etc.). The tensile strength of steel wire can be increased by wire drawing work hardening.

The invention described in Japanese Patent Laid-Open No. 2000-107943 specifies the upper limit of the thickness of copper and the range of the thickness of zinc that are sequentially coated on the surface of a high carbon piano wire having a wire diameter of 0.03 to 0.1 mm. By doing so, it is intended to provide an inexpensive electrode wire which has a high tensile strength that can be used in place of the heavy metal wire and has a performance equal to or higher than the electric discharge machining performance such as machining speed. And, in paragraph [0016] of this publication, regarding the tensile strength, "the outer diameter is φ0.
05mm electrode wire ・ ・ ・ Tensile strength is 2170N / mm ²
Met. It is described as ".

The invention described in Japanese Patent Laid-Open No. 2000-198027 discloses an electrode wire in which a brass coating is formed on a steel wire having a wire diameter of 0.03 to 0.3 mm and a tensile strength of 150 to 250 kgf / mm ^2. As a prerequisite technology, the processing rate (electrical conductivity) and tensile strength are made excellent by specifying the proportion of copper in the whole brass and the copper composition, and by specifying the carbon component of the steel wire, and the strength of the core wire is high. It is intended to provide an electrode wire having a thick outer brass. In paragraph [0012] of this publication, "the upper limit of the tensile strength of the wire drawing process for the electrode wire is 400 to 500 kgf / mm ² ," is described.

[0009]

However, when electric discharge machining is performed using an electrode wire having a steel wire as a core and having a small wire diameter and high tensile strength as described in the above publication, the electrode wire is There was a case where the frequency of the machine became large and sometimes the wire was broken. The increase in the frequency of the electrode wire and the disconnection adversely affect the dimensional accuracy of the work piece and the surface roughness of the cut surface.

Therefore, as a result of intensive studies on the cause of the increase in the frequency of electric discharge and the cause of wire breakage, the present inventor considers the tension applied during electric discharge machining and determines the range of the tensile strength in the optimum range. The inventors have found that the frequency can be suppressed to a low level by adjusting to, and the disconnection due to the decrease in toughness can be eliminated, and the present invention has been completed.

Therefore, the present invention provides an electrode wire that suppresses an increase in the frequency of electric discharge machining, which is a factor that hinders the stability of electric discharge machining, eliminates disconnection, and improves electric discharge machining performance. It is an issue.

[0012]

A wire for electric discharge machining according to the present invention is an electrode wire having a steel wire having a wire diameter of 0.02 to 0.20 mm as a core material, and a tensile strength Ts of the following formula. In addition, the core wire is provided with a plating layer having a two-layer structure consisting of a brass-plated lower layer and a zinc-plated upper layer. [Equation 1] (−2500d + 3000) MPa ≦ Ts ≦ (−250
0d + 4500) MPa Ts: Tensile strength (MPa) d: Electrode wire diameter (m
m)

In the electrode wire of the present invention, the core material is a steel wire, and the tensile strength is specified as described above, so that the increase in the frequency and the disconnection of the frequency during the electric discharge machining, which are the factors that hinder the stability of the electric discharge machining. Can be eliminated, and the electric discharge machining performance can be improved.

By the way, in the above construction, the reason why the wire diameter of the steel wire is 0.02 to 0.20 mm is that if it is less than 0.02 mm, the tensile strength becomes insufficient, and the dimensional accuracy and the cut surface of the workpiece are reduced. 0.20 because the improvement of the surface roughness of
This is because if the diameter exceeds mm, the precision-machined component cannot be processed with high precision when the wire diameter is too large and the size and shape are minute. In order to further improve the electric discharge machining performance, the wire diameter of the steel wire is more preferably 0.02 to 0.10.

Further, the tensile strength Ts is (-2500d +
3000) to (-2500d + 4500) MPa is used because, if it is less than (-2500d + 3000) MPa, the tensile strength is insufficient and the dimensional accuracy of the workpiece and the surface roughness of the cut surface cannot be improved. (-2500d + 4
If it exceeds 500) MPa, the tensile strength becomes too high,
The toughness deteriorates and induces wire breakage during electrical discharge machining.
This is because the frequency increases and the surface roughness and processing accuracy of the work piece deteriorate.

As the steel wire used for the electrode wire of the present invention,
There are hard steel wires, piano wires, etc., as defined in JIS. Further, considering the tensile strength of the electrode wire, the carbon content needs to be 0.5% by weight or more, but is preferably 1.2% in view of wire drawing workability.

The surface of the electrode wire is provided with a plating layer having a two-layer structure consisting of a brass-plated lower layer and a zinc-plated upper layer. Since brass plating contains copper, it improves the electric conductivity of the electrode wire, and since it contains zinc, it has excellent affinity with the zinc plating layer provided on top of it, and enhances the bond strength between the brass plating and zinc plating. Further, in the galvanized layer, zinc is sublimated by the heat generated at the time of electric discharge machining, and the heat absorption due to the sublimation can suppress the temperature rise of the processed part.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, an electrode wire 1 of the present invention is a hard steel wire having a carbon content of 0.79 to 0.86% by weight or a piano wire having a carbon content of 0.80 to 0.85% by weight. The wire is a core material 2, and the surface of the core material 2 is provided with a plating layer having a two-layer structure including a brass-plated lower layer 3 and a zinc-plated upper layer 4. The diameter of the electrode wire 1 is 0.02 to 0.2.
At 0 mm, the tensile strength Ts is (-2500d + 300
0) to (-2500d + 4500) MPa.

In the electrode wire of the present invention, an ordinary wire having a diameter of 5.5 mm is subjected to patenting and drawing to obtain a desired wire diameter, and this wire is plated with copper and then zinc. It can be obtained by applying brass plating after heat treatment, and then zinc plating the upper layer.
With the patenting and wire drawing in the above manufacturing process,
The wire may be finished to a wire diameter of about 1 to 1.0 mm, brass-plated on this wire in the same manner as above, and then drawn to a desired wire diameter, which may be galvanized. . Since brass plating improves wire drawing workability, it enables high speed wire drawing. The wire diameter for brass plating is determined from the final wire diameter and tensile strength.

The final wire diameter is 0.02 to 0.20 mm and is determined according to various processed products and processed shapes. Further, the tensile strength can be adjusted by the C content of the original wire, the wire diameter and temperature when the final patenting treatment is applied, the area reduction rate in the final wire drawing step, and the like.

[0021]

[Example] Carbon content of wire diameter 5.5 mm 0.82% by weight
Repeatedly patenting and wire drawing the piano wire of
After manufacturing an intermediate wire with a wire diameter of 0.1 to 1.0 mm, applying copper / zinc plating to this intermediate wire, heat-spreading it to brass plating, and drawing it again to have various wire diameters. An electrode wire rod was obtained. Next, this electrode wire material was galvanized to manufacture electrode wires of various wire diameters. Then, using these electrode wires, a through hole was processed into a super hard material, and the dimensional accuracy and surface roughness were compared. The copper plating and zinc plating were electroplating, and the thicknesses of the brass plating layer and the zinc plating layer of the finished electrode wire were 4.5 μm and 2.5 μm, respectively. The results are shown in the graph of FIG.

In the figure, ● indicates that the dimensional accuracy and surface roughness of the workpiece, which is a carbide, are the same as or lower than conventional ones, ×
Indicates that disconnection occurred during electric discharge machining, and ○ indicates that there were no problems in all points. From the graph shown in FIG. 2, the tensile strength is (-2500d + 3000) to (-2500d).
Within the range of +4500 MPa, no wire breakage occurs,
It can be seen that the dimensional accuracy and surface roughness of the workpiece are improved.

[0023]

EFFECT OF THE INVENTION The electrode wire of the present invention has high conductivity and discharge stability, and also has high tensile strength, so that it can be applied with high tension by an electric discharge machine, and particularly precision equipment. It enables minute and high-precision machining of the parts that make up. Further, since the disconnection during the electric discharge machining can be eliminated and the vibration of the electrode wire can be further suppressed, the dimensional accuracy of the component and the surface roughness of the cut surface can be remarkably improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of an electrode wire of the present invention.

FIG. 2 is a graph showing tensile strength at various wire diameters and evaluation thereof.

[Explanation of symbols]

1 electrode wire 2 core material 3 Brass plating layer 4 Galvanized layer

Claims (2)

[Claims] 1. An electrode wire comprising a steel wire having a wire diameter of 0.02 to 0.20 mm as a core material, a tensile strength Ts satisfying the following equation, and a brass-plated lower layer on the surface of the core wire. An electrode wire for wire electric discharge machining, comprising a plating layer having a two-layer structure including an upper layer of zinc plating. [Equation 1] (−2500d + 3000) MPa ≦ Ts ≦ (−250
0d + 4500) MPa Ts: Tensile strength (MPa) d: Electrode wire diameter (mm) 2. The electrode wire for wire electric discharge machining according to claim 1, wherein the wire diameter is 0.02 to 0.10 mm.