JPH0435543B2 - - Google Patents

Description

[Detailed description of the invention]

Technical Field The present invention relates to an electrode wire for wire electrical discharge machining. Background technology Wire electrical discharge machining (hereinafter simply referred to as electrical discharge machining)
The method involves causing electrical discharge to occur between the workpiece and an electrode wire for wire electrical discharge machining (hereinafter referred to as the electrode wire) using a machining liquid such as water as a medium, and then making the electrode wire and the workpiece relative to each other. This is a conventional method in which the workpiece is cut into a desired shape by moving the workpiece. In this electric discharge machining method, a long wire having a diameter of usually 0.03 to 0.25 mm is prepared as the electrode wire, and new wires are sequentially supplied to the electric discharge machining area. Conventionally, electrode wires include hard copper wire, brass wire, tungsten wire, Zn or Al coated brass wire, 0.1 to 4%
Al-20 to 38% Zn-Cu alloy wire is used, but hard copper wire and brass wire are subject to limitations in machining speed and dimensional accuracy due to electrode components adhering to the machined surface during discharge. Although tungsten wire has a low electrical discharge machining speed and good surface finish and dimensional accuracy, it is difficult to manufacture and expensive. Brass wire coated with Zn or Al is coated with a low melting point metal, so when the electrode wire is cut into a needle shape using flame etc. in order to pass it through a die during electrical discharge machining, the tip ends up in a ball shape. This makes it difficult to pass through a die, resulting in poor workability.Furthermore, the coating layer has lower tensile strength than the core material, resulting in poor processing accuracy. 0.1~4%Al−20~38%Zn−
Cu alloy wire has poor wire drawability compared to ordinary brass wire, and depending on electrical discharge machining conditions, a large amount of copper may transfer or adhere. Composition of the Invention The present invention has been made to eliminate the above-mentioned drawbacks, and it is extremely easy to manufacture and draw an electrode wire, has high mechanical strength, can take high tension during electrical discharge machining, and has high processing accuracy. The rough surface has a large surface area and good wettability with water, and the accompanying cooling effect increases processing speed.The surface has a high concentration of low-melting metal elements, which prevents electrode components from adhering to the processed surface. In addition, the part with a low melting point is extremely thin, so when cutting the electrode wire,
It is an object of the present invention to provide an inexpensive electrode wire that has good workability when passed through a die because no ball formation occurs at the tip. Note that the reason why the surface of the electrode wire described above is rough is that the surface layer is made of, for example, an alloy with a high Zn concentration, and the surface layer has low ductility, causing surface roughness during wire drawing. That is, for the electrode wire of the present invention, for example, a copper alloy wire as a raw material is drawn, and then passed through a molten metal of a low melting point metal or an alloy of the metal, so that the low melting point metal or alloy is coated on the copper alloy wire. After wiping off the partially adhered wire with asbestos or the like, the wire is further drawn and annealed to diffuse and eliminate the adhered low melting point metal or alloy within the copper alloy wire. It can also be easily manufactured by heating in an inert gas atmosphere after forming a low melting point metal layer. The low melting point metal elements used in carrying out the present invention are preferably those having a melting point of 150 to 700°, such as Bi, Sb, Zn, Cd, Pu, In, Sn, Pb, Mg, or Al. It is. Although alkali metals such as K, Na, and Rb have low melting points, they cannot be used because they react violently with water, which is the medium for electrical discharge machining. Also,
Mercury, which is liquid at room temperature, is highly toxic and unsuitable. Among the above elements, which have a melting point of 150 to 700°C, Cd is somewhat problematic in terms of toxicity, and Pu is unsuitable because it is expensive and has radioactivity. Therefore, the elements that are practically used are Bi, Sb, Zn, In,
Limited to Sn, Pb, Mg or Al. As shown in FIGS. 1 and 2, the electrode wire thus obtained has a higher concentration of the low melting point metal element on the outer surface and a correspondingly lower concentration of the copper element, and this tendency reverses as it approaches the center layer. Here, it is desirable that the copper element concentration at the outermost surface be 0.1 to 5%, and that the overall copper element concentration be 61 to 95%. The reason why the copper element concentration in the surface layer was limited to 0.1 to 5% was 0.1%.
If the concentration is below 5%, the concentration of low-melting metal elements is high, and when the electrode wire is cut during passing through the die, a ball will be formed at the tip, making it difficult to pass through the die. The amount of copper deposited increases and the finished surface condition deteriorates. Next, the reason why the overall copper element concentration was limited to 61-95% is that below 61%, the conductivity is low and the electrical discharge machinability is poor, while above 95%, the tensile strength is low and the tension during electrical discharge machining is low. As a result, machining accuracy deteriorates. The features of the present invention will be summarized below. As described in the conventional example, the presence of a low melting point alloy element on the surface is certainly highly effective in suppressing electrical discharge machinability, particularly the phenomenon in which electrode components adhere to the workpiece during electrical discharge. However, when the surface is formed of a single low-melting point metal layer, the low-melting point metal is considerably consumed by discharge, and a thickness of considerably preferably 10 μm or more is required to exhibit the effect. This results in a decrease in processing accuracy due to the aforementioned decrease in tensile strength, and a deterioration in workability due to ball formation during flame cutting. The present invention maintains the adhesion prevention effect by increasing the low melting point metal element concentration on the outer surface, which has a greater influence on the adhesion phenomenon, and suppresses consumption due to discharge by increasing the Cu concentration toward the inside of the conductor. Moreover, since the layer with a high concentration of low melting point metal having low tensile strength is limited to the extreme surface, there is almost no decrease in tensile strength and, of course, there is no problem of ball formation. If the Cu element on the outermost surface is 0.1 to 5%, it will not have any adverse effect on adhesion. Due to its high tensile strength, high tension can be applied during processing, which further results in reduced adhesion. Hereinafter, the electrode wire of the present invention will be explained based on Examples. Examples Example 1 A 1.0 mmφ 70% Cu-30% Zn brass wire shown in Invention No. 2 was passed through molten Zn (temperature 450°C) for 5 seconds, and then squeezed out with asbestos. The wire was drawn to 0.5 mmφ. Next, after annealing at 500°C for 24 hours, the wire was further drawn to obtain an electrode wire with a diameter of 0.2 mm. When cutting 25mm thick SKD-15 tool steel using this electrode wire,
The processing speed ratio is 180 when the conventional hard copper wire is set as 100.
A good result was obtained with a ratio of copper adhesion to the processed surface of 20. Furthermore, when cutting the electrode wire when passing it through the die, no ball was formed at the tip, and the electrode wire could be passed through the die smoothly. Example 2 A 0.8 mmφ 65% Cu-35% Zn brass wire shown in Invention No. 5 was electroplated with 8 μm of Sn. After that, the wire was drawn to 0.5 mmφ. next,
After diffusion annealing at 270℃ for 2 hours, it was further wire drawn.
An electrode wire with a diameter of 0.2 mm was obtained. 25 using this electrode wire
When cutting mm-thick SKD-15 tool steel, the machining speed ratio was 160, and the ratio of copper adhesion to the workpiece surface was 45, with the conventional hard copper wire being 100.
Furthermore, when cutting the electrode wire when passing it through the die, no ball was formed at the tip, and the electrode wire could be passed through the die smoothly. In addition, in both Examples 1 and 2, brass wires of 1.0φ and 0.8φ, which are the raw materials for the electrode wires, could be obtained from a base material of 5 mmφ without intermediate annealing. Comparative Example 1 65% Cu-33% Zn- of 1.0 mmφ shown in Comparative Example No. 2
25mm thick SKD-15 was made using 0.2mmφ electrode wire obtained by drawing 2% Al wire and repeating the heat treatment process several times.
When tool steel was cut, the machining speed ratio was 160 when the conventional hard copper wire was set at 100, and the copper adhesion ratio to the workpiece surface was 70. Three intermediate annealing treatments were required to draw the wire to 1.0 mmφ from the material. Comparative Example 2 After passing the 1.0 mmφ 70% Cu-30% Zn brass wire shown in Comparative Example No. 1 through molten Zn (430°C) for 5 seconds, the wire was directly stretched without tightening the Zn attached to the surface. An electrode wire with a diameter of 0.2 mm was obtained. Using this electrode wire
When cutting 25mm thick SKD-15 tool steel, the machining speed ratio was 160 when the conventional hard copper wire was 100.
Although the ratio of the amount of copper deposited on the surface to be machined was 20, a ball of 0.3 mmφ was formed at the tip during cutting when passing through the die, making the process of passing through the die extremely difficult. These results are shown in Table 1.

[Table] As can be seen from Table 1, electrode wires of the present invention No. 1~
No. 6 has a copper element concentration on the outermost surface in the range of 0.5 to 15%, and has good die passing workability and electrical discharge machining characteristics (machining speed, amount of copper deposited on the surface to be machined). Comparative Example No. 1 has excellent electrical discharge machining properties, but has poor die threading workability, and Comparative Example No. 2 has poor wire drawability, so many intermediate annealing steps were required before producing the electrode wire. However, there is a disadvantage that there is a large amount of copper deposited on the surface to be machined during electrical discharge machining. Effects As described above, the electrode wire according to the present invention is easy to manufacture, has good workability through the die, and has good electrical discharge machining characteristics, and therefore has a remarkable effect of reducing running costs in electrical discharge machining. It is something that can be demonstrated.

[Brief explanation of drawings]

FIGS. 1 and 2 are diagrams showing examples of concentration distributions of low melting point metal elements and copper elements in the diametrical direction in a longitudinal section of the wire electric discharge machining electrode wire of the present invention. The horizontal direction indicates the position, and the vertical direction indicates the concentration of the low melting point metal or copper.

Claims (1)

[Claims] 1. The concentration of the low melting point metal element contained in the metal wire is
A copper alloy electrode wire for wire electrical discharge machining, characterized in that at least the surface layer is higher as the outer surface of the metal wire becomes higher. 2 Low melting point metal elements include Bi, Sb, Zn, In, Sn,
The copper alloy electrode wire for wire electrical discharge machining according to claim 1, characterized in that it is made of Pb, Mg or Al. 3. The copper alloy electrode wire for wire electrical discharge machining according to claim 1 or 2, characterized in that the overall Cu element concentration is 61 to 95%. 4. The copper alloy electrode wire for wire electrical discharge machining according to claim 1, 2, or 3, characterized in that the Cu element concentration on the outermost surface is 0.1 to 5%.