JPS60249529A - Composite electrode wire for wire-cut electrical-discharge machining - Google Patents

Abstract

PURPOSE:To increase the working speed, improve working accuracy, and permit cost cut by applying copper-zinc alloy having a specific thickness or more onto the periphery of a hardsteel wire through adhesion. CONSTITUTION:The thick copper-zinc alloy having a thickness exceeding 20mu is applied through adhesion onto the periphery of a hard steel wire. In case of 20mu or less, the copper-zinc alloy layer is molten and dispersed during electrical discharge machining, and the steel wire is expsed and molten, and a part of the steel wire is martensite-transformed and becomes brittle, and wire breakage often occurs. When barium, strontium, cesium are added into the copper-zinc alloy, and further the surface is applied with zinc, cadmium, aluminum or the alloy thereof, electrical discharge characteristic can be improved, and working speed can be increased markedly, and the working accuracy can be improved by increasing the tensile strength of the electrode wire without giving an influence onto the machining performance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Background and Objects of the Invention] The present invention relates to a composite electrode wire for wire-cut electrical discharge machining, and particularly to a composite electrode wire for wire-cut electrical discharge machining having a strength close to that of a tungsten electrode wire.

[Using an electrode wire and subjecting this electrode wire to stress] Wire-cutting a method of electric discharge machining by applying pulse discharge to a gap between two bodies facing each other with a minute gap!・It is called electrical discharge machining. This wire-cut electrical discharge machining is currently widely used because it can continuously and accurately machine press molds and other complex-shaped workpieces.

By the way, with regard to wire-cut electrical discharge machining, there has recently been a strong demand for faster acceleration and improved machining accuracy.In order to meet these demands, the following structural improvements have been made to the electrode wire. is required. In other words,
The demand for higher speeds in two-speed processing requires improved discharge characteristics, and the demand for improved machining accuracy requires ultra-thin wires.

The electrode wire that is currently commonly used is brass wire, but this brass wire has a tensile strength of about 60/r9/mm2 at most, so when performing electrical discharge machining using this brass wire, machining accuracy is If the wire diameter is made thinner or the tension is increased in order to improve performance, there is a risk that the brass wire will break.

When brass wire is used, it is difficult to improve processing accuracy due to limitations.

In addition, some tungsten wires are used as electrode wires, but this tungsten wire has greater tensile strength than brass wires, so it can be made into ultra-thin wires, which improves processing accuracy. can be achieved.

However, the cost of tungsten wire is very high, and therefore its use is limited to only a few places.The purpose of the present invention is to eliminate the drawbacks of the prior art described above, and to increase the processing accuracy and the accuracy of processing. It is an object of the present invention to provide a composite electrode wire for wire-cut electrical discharge machining that can improve the performance and is inexpensive.

[Summary of the Invention] That is, the gist of the present invention resides in a composite electrode wire for wire-cut electrical discharge machining, in which a thick copper-zinc alloy with a thickness exceeding 20 μm is adhesively coated on the circumference of a hard steel wire.

In the above, the reason why the thickness difference of the copper-zinc alloy was made to be more than 20μ is because if it is less than 20μ, the steel-zinc alloy layer will melt and scatter during electrical discharge machining. 4 wire may be exposed and melted, and in this case, a portion of the steel wire undergoes martenzite transformation and becomes brittle, resulting in frequent breakage during processing. If the thickness of the copper-zinc alloy exceeds 20 μm, disconnection due to melting and scattering of the copper-zinc alloy layer will not occur.

Regarding this point, the diameter was manufactured by adhesively coating 7/3 brass (30% Zn-Cu alloy) as a copper-zinc alloy on the circumference of a hard steel wire, and varying the thickness in the range of 1 to 50μ. 0
．． There are experimental results of electrical discharge machining using composite electrode wires of 2 mmφ, which are shown in Table 1.

As you can see from Table 1, the thickness of the above brass is 20μ
It can be seen below that the number of wire breaks during processing is steadily increasing.

Table 1 (The number of disconnections is the number of times per 1 hour) The present invention also shows that by adding barium, strontium, and cesium to the copper-zinc alloy, the discharge characteristics can be improved, thereby significantly increasing the machining speed. can. Although the cause of this is not clear at present, it is thought that the added elements all have low melting points and high vapor pressures.

Regarding the improvement of the discharge characteristics, the discharge characteristics can also be significantly improved by plating the surface of the copper-zinc alloy with zinc, cadmium, aluminum or an alloy thereof. The reason for this may be similar to that of upper air. In order to improve the discharge characteristics, the plating thickness must be at least 0.571, and the plating may be either hot-dip plating or electroplating.

As a method for coating the circumference of a hard steel wire with a thick copper-zinc alloy having a thickness of more than 20 μm, the following method is available, although not particularly limited.

(1) A method of hot extruding or isostatically extruding a composite billet of hard steel and copper-zinc alloy and drawing it into a wire. (2) A method of vertically stretching a copper-zinc alloy tape around the circumference of a hard steel wire and drawing it at the seam. (3) A method of hot extrusion coating a copper-zinc alloy around the circumference of a hard steel wire and drawing the wire.

[Embodiments] Next, embodiments of the present invention will be described with reference to the accompanying drawings.

Example (1) Hard steel wire with a wire diameter of 5Mφ (J I 5350G, -8WRH
32B, c=6.32%, Mn=0.7%, Si-0,
2%) was inserted into a 7/3 brass pipe with an outer diameter of 8rNnφ and a wall thickness of 0.8mmt, which was first drawn and annealed to an outer diameter of 2.6mmφ, then drawn and annealed to an outer diameter of 1.2mmφ,
Finally, the wire was drawn to an outer diameter of 0.2 mm, thereby producing a composite electric fi wire consisting of a brass-coated hard steel wire with a brass coating thickness of 22 to 27 μm.

FIG. 1 and FIG. 2 respectively show a scanning electron micrograph of the surface and a cross-sectional micrograph of the composite electrode wire manufactured by the method described in -V. This shows that the composite electrode wire has a very smooth surface and a substantially uniform brass coating thickness in the range of 22 to 27 microns.

Example (2) 7/3'IA copper was dissolved and 1 part by weight of 3a, C3°3
Three types of billets made of the respective alloys were prepared by wrapping each of the respective alloys in copper foil, adding them to the molten metal, and then casting them into a mold.

Extrude each of these billets 1 to 8 mm in outer diameter.
A copper-zinc alloy vibe with a wall thickness of 0.8 mj was manufactured.

Using this copper-zinc alloy vibrator, three types of composite electrode wires each having an outer diameter of 0.2 mmφ and a copper-zinc alloy coating thickness of 22 to 27 μm were manufactured in the same manner as in (1) above.

Example (3) Zinc, cadmium, and aluminum were each plated to a thickness of 1 μm by hot-dip plating on the surface of a composite electrode wire made of brass-coated hard steel wire produced by the method (1) above.

Table 2 shows the tensile strength and conductivity of the composite 11M wires produced by the methods of Examples (1), (2>, and (3)). According to this table, the tensile strength is It can be seen that the composite electrode wire according to the embodiment of the present invention has approximately twice the strength of the conventional 7/3 brass wire.

Tables 2 and 3 show experimental results when each of the composite electrode wires manufactured by the methods of Examples (1), (2), and (3) above was used for the discharge power loe.

A steel material with a thickness of 25 m was used as the workpiece, and electrical discharge machining was carried out under the conditions of a power supply voltage of 130 μ, a wire tension of 800 SF, and 1500 g. The test results are based on machining speed, surface condition,
The processing speed was evaluated in terms of dimensional accuracy, with the speed obtained with 7/3 brass wire being set as 100, and compared with that.

According to Table 3, the composite electrode wire according to the embodiment of the present invention is:
It can be seen that the processing speed is faster than the conventional 7/3 brass wire, and the surface condition and dimensional accuracy are also better. In particular, when the wire tension is 1500 g, conventional 7/3 brass wire breaks frequently, but the composite electrode wire described in I has no breakage, has a good surface condition, and has a dimension of M. What you can do changes.

Table 3 [Effects of the Invention] As is clear from the above explanation, according to the composite electrode wire of the present invention, a thick copper layer with a thickness of more than 20μ is formed around the hard steel wire.
Since the structure is coated with zinc alloy, the presence of the thick steel-zinc alloy increases the tensile strength of the electrode/electrode wire without affecting the discharge characteristic d5 and workability (cutting, etc.), thereby improving machining accuracy. can be significantly improved. In addition, if an element that can improve the discharge characteristics is added to the copper-zinc alloy, or a metal that can improve the discharge characteristics is plated on the surface of the copper-zinc alloy, it is possible to improve the machining viscosity. Speed can be increased. Furthermore, since the composite electrode wire of the present invention does not use tungsten, it is inexpensive and very practical.

[Brief explanation of drawings]

FIG. 1 shows a part of the surface of a composite electrode wire for wire-cut electrical discharge machining according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the composite electrode wire. Micrograph 1j (150x magnification). 1st item Ya 2ω 1゜4, Agent 〒100 Telephone Tokyo ('216) 1 (ill I smoke) Column for detailed explanation of the invention, column for brief explanation of drawings, and column for brief explanation of drawings in the specification subject to amendment Figures 1 and 2. Contents of the amendment (1) On page 7, lines 8 to 9 of the specification, the phrase [scanning electron micrograph of the surface and micrograph of the cross section] has been changed to “
Corrected to ``Partial front view and cross-sectional view.'' (2) On page 12, lines 5 to 1 of Laxatives are corrected as follows: "FIG. 1 is a partial front view of a composite electrode wire for wire-cut electric discharge machining according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of the composite electrode wire." (6) First of the drawings Figure and second
Correct each figure as shown in the attached sheet. Catalog of attached documents 1 or more copies

Claims (3)

[Claims] (1) Thick copper with a thickness of over 20μ on the circumference of the hard copper wire.
A composite electrode wire for wire-cut electric discharge machining characterized by being adhesively coated with zinc alloy. (2) The composite electrode wire for wire-cut electric discharge machining according to claim 1, wherein the copper-zinc alloy is made of an alloy containing barium, cesium, and strontium. (3) Zinc, cadmium,
The composite electrode wire for wire-cut electric discharge machining according to claim 1 or 2, characterized in that it is plated with aluminum or an alloy thereof.