JPH0249851B2 - WAIYAKATSUTOHODENKAKOYOWAIYADENKYOKU - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a wire electrode used in wire cut electrical discharge machining. [Prior Art] Generally, the electrode material of the wire electrode used in wire cut electrical discharge machining has a diameter of 0.05 to 0.3.
There are those made of mm copper, brass, or tungsten. The state of electric discharge machining when these wire electrodes are used will be explained with reference to FIG. First, tension is applied to the wire electrode 1 and the wire electrode 1 is fed at a constant speed in the direction of the arrow A in the figure while facing the workpiece 2. Next, a pulse voltage is applied between the wire electrode 1 and the workpiece 2 while spraying the machining liquid 3 coaxially with the wire electrode 1 . As a result, electrical discharge is repeated in the opposing micro-gap using the machining fluid 3 as a medium, and the workpiece 2 is melted and scattered by the thermal energy generated during the electrical discharge. Wire electrode 1 to keep the opposing micro-gap constant and continuously perform discharge
The relative movement of the workpiece 2 and the workpiece 2 is usually controlled numerically using an XY cross table (not shown). By repeating the discharge as described above and controlling the XY cross table, the machined grooves 4 are continuously formed. In this way, it is possible to process any shape, and it is widely applied to general mold punching, cutting, etc. Furthermore, the processing speed of the wire cut depends on the tension applied to the wire electrode 1, as shown in FIG. That is, the tension T (g) that applies the horizontal axis,
If the vertical axis is the machining speed F (mm ² /min), as shown in the figure, there is a characteristic that slopes upward to the right, and it can be seen that the greater the tension, the faster the machining speed. This is because as the tension increases, the vibration of the wire electrode 1 decreases, making it possible to uniformly control the opposing micro-gap dimensions, and as a result of being able to repeat stable electrical discharge, the machining speed increases. It has been confirmed that this will happen. [Problems to be solved by the invention] Conventional wire electrodes 1 made of copper, brass, steel, etc. having a crystalline structure have a limit in improving their own tensile strength, and the processing speed can be improved by increasing the tension. I can't hope to. In addition, when using a conventional wire electrode 1 made of copper, brass, steel, etc., and feeding the workpiece 2 from top to bottom or from bottom to top as shown in FIG. A part of the wire electrode 1 is scattered and attached to the upper or lower part of the machining groove 4 of the workpiece 2 by electric discharge. The main components of this deposit 5 are copper and steel, and it is observed that the deposit 5 is not deposited on the front and side surfaces of the wire electrode 1 as shown in Fig. 3A, but is mostly deposited on the rear part. . If such deposits 5 remain on the machined surface, the dimensional accuracy will be significantly impaired, and in areas where machining energy is high, the thickness may reach about 10 to 100 μm. If the machining energy is further increased, deposits 5 may fill the machining grooves 4, as shown in FIG. This phenomenon occurs not only because the workpiece does not fall out, but also because the machining fluid 3 jetted coaxially with the wire electrode 1 does not penetrate into the opposing micro-gap, causing an air discharge phenomenon and reducing the machining speed. This may cause the wire electrode 1 to become disconnected. The main components of these deposits 5 are copper or iron, so in order to remove them, dangerous chemicals such as fuming nitric acid must be used in the removal process, which is both inefficient and extremely dangerous. The problem was that they were forced to do so. As described above, the conventional wire electrode 1 has various drawbacks. The present invention has been made in view of the above-mentioned drawbacks, and it is an object of the present invention to provide a wire electrode that has very small deposits, can be processed at high processing speed, and can be processed with high precision. [Means for Solving the Problems] The wire cut wire electrode for electric discharge machining according to the present invention heats the surface of an amorphous metal wire made of pure metal or an alloy, so that the core portion of the wire is made of amorphous metal, The above-mentioned problems were solved by making the surface thin layer of crystalline metal and coating the surface with a highly conductive material. [Function] In the present invention, by constructing a wire using various pure metals or alloys in an amorphous state, a wire electrode with improved tensile strength can be obtained. Furthermore, by making various metals amorphous, the electrical conductivity decreases, but by crystallizing only the wire surface, the electrical conductivity can be compensated for with almost no reduction in the strength (tensile strength) of the amorphous metal wire. Furthermore, by coating the surface of the wire electrode configured as described above with a highly conductive material, the conductivity can be further improved. [Example] The present inventors rapidly cooled a pure metal or alloy from a molten state by an ultra-quenching method such as spinning in a rotating liquid to create a fine amorphous wire, and used the wire as a wire electrode. The present inventors have discovered that by further drawing a thin amorphous wire into a wire electrode, it is possible to obtain a wire electrode having a tensile strength incomparably greater than that of conventional wires. Generally, the tensile strength of an amorphous metal wire is 1.5 to 3 times that of a crystalline metal wire. As an example, amorphous metal (Fe ₇₅ Si ₁₀ B ₁₅ ) wire A
FIG. 5 shows the stress-strain curve of the conventional piano wire B. However, in general, when a metal material is made into an amorphous state, its electrical resistance increases, and this tendency is particularly pronounced in transition metals, making it undesirable as a wire electrode for wire-cut electrical discharge machining. Therefore, in order to improve the conductivity of the wire without losing the good mechanical properties (increased tensile strength) obtained by making it amorphous, the surface of the amorphous metal wire is coated with a thin crystalline layer. If such a wire is used, the two requirements of tensile strength and electrical conductivity can be satisfied. By the way, since it is desirable that the wire electrode has good conductivity, it is also effective to coat the surface of the wire with a conductive material. That is, as shown in FIG. 6, the processing speed can be further improved by coating the wire 6, which is an amorphous metal wire whose surface has been crystallized, with a highly conductive material 7. On the other hand, since the wire electrode is made of copper or a copper-based alloy, even if the wire is amorphous, in the case of a copper-based metal, a part of the wire electrode is scattered and attached to the machined surface of the workpiece due to electric discharge. This also applies to steel-based wire electrodes, and this tendency is particularly pronounced when the surface is a thin crystalline layer. Therefore, in order to eliminate this adhesion phenomenon, as shown in FIG. 7, a wire 6 whose surface has been crystallized is coated with a highly conductive material 7, and further coated with zinc, magnesium, and tin. ,lead,
Similarly, an amorphous metal wire electrode coated with a multilayer coating of metal such as aluminum or cadmium or alloy 8 can also improve processing accuracy, adhesion, and processing speed. In this way, amorphous metal wire electrodes manufactured by rapidly cooling molten metal have a tensile strength 1.5 to 3 times higher than conventional crystalline metal wire electrodes, and can be used to increase tension during actual processing. Therefore, machining speed is improved. Generally, when a metal material is made amorphous, its conductivity decreases, but in order to improve this, the surface of the amorphous metal wire is heated using, for example, a high-frequency heating device, and a very thin layer near the surface is crystallized. By restoring the conductivity, a two-layer wire electrode structure is created in which the core portion of the wire is made of amorphous metal and the thin surface layer portion is made of crystalline metal. This results in the high tensile strength required for wire electrodes,
A wire electrode having good conductivity can be obtained. In addition, heating methods include high-temperature bathtub,
Various methods such as laser and gas burner are possible. Further, even in the case of an amorphous metal wire electrode, for example, if it is a wire electrode whose main component is copper, a part of the electrode will adhere to the workpiece. In order to prevent that,
Zinc, magnesium, tin, etc. on the surface of the wire electrode.
By coating the surface with metals such as lead, aluminum, cadmium, or alloys thereof, adhesion can be almost eliminated, machining accuracy can be improved, and machining speed can also be increased. For reference, a conventional brass wire electrode was coated with zinc to a thickness of approximately 10 μm using the plating method, and the effect when actually processing steel material was compared with that of conventional brass and steel wire electrodes. The results are shown in Table 1, expressed as a percentage based on the characteristics of brass, with the processing conditions unified. This shows that the zinc coating has a great effect on the adhesion phenomenon and on improving the processing speed. It is clear that this effect remains the same even if the core wire is an amorphous metal wire.

[Table] Note that the metal used for the wire electrode of the present invention may be any type of metal as long as it can be made amorphous (non-crystalline). [Effects of the Invention] As described above, the present invention has the advantage that it is possible to obtain a wire cut wire electrode for electric discharge machining that has very small deposits, can be processed at high processing speed, and can be processed with high precision.

[Brief explanation of drawings]

Figure 1 is a diagram showing the state of wire cut discharge, where A is a diagram seen from the wire axis direction, B is a diagram seen from a direction perpendicular to the wire axis, and Figure 2 is a diagram showing the relationship between wire electrode tension and machining speed. Figures 3 and 4 are diagrams showing the state of attachment of the electrode material of a conventional wire electrode to the workpiece surface, where A is a view viewed from the wire axis direction, and B is a view from the wire axis direction. 5 is a diagram showing an example of stress-strain curves of an amorphous wire and a piano wire, and FIG. 6 is a sectional view showing an example of a wire electrode according to the present invention.
FIG. 7 is a sectional view showing another embodiment. In the figure, 1 is a wire electrode, 2 is a workpiece, 3 is a machining fluid, 4 is a machining groove, 5 is a deposit, 6 is a wire electrode material, 7 is a highly conductive material, and 8 is a coating metal or alloy. be. Note that the same reference numerals in the figures represent the same parts.

Claims (1)

[Claims] 1. By heating the surface of an amorphous metal wire made of pure metal or alloy, it is possible to make the core of the wire an amorphous metal, the thin surface layer a crystalline metal, and further coat the surface with a highly conductive material. Characteristic wire electrode for wire cut electrical discharge machining.