JPH026819B2 - - 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, molybdenum, or tungsten. The state of electrical discharge machining using these wire electrodes will be explained with reference to FIG. First, tension is applied to wire electrode 1, and arrow A in the figure
It is made to face the workpiece 2 while being fed at a constant speed in the direction. Next, while spraying the machining liquid 3 in the coaxial direction of the wire electrode 1, the wire electrode 1 and the workpiece 2 are
A pulse voltage is applied between them. As a result, electric discharge is repeated using the machining fluid 3 as a medium in the opposing micro-intervals, and the workpiece 2 is melted and scattered by the thermal energy generated during the electric discharge. In order to keep the opposing microscopic distance constant and to continuously perform electric discharge, the relative movement of the wire electrode 1 and the workpiece 2 is usually controlled numerically using an XY cross table (not shown). By repeating electrical discharge as described above and controlling the XY cross table, the machining groove 4 is continuously formed, allowing machining of any shape, and is widely applied to general mold punching, cutting, etc. When a conventional wire electrode 1 made of, for example, copper or brass is used, as shown in FIG. A part of the wire electrode 1 is scattered and attached to the upper or lower part of the machined groove 4 of No. 2 due to electric discharge. In this case, the main component of the deposit 5 is copper, and the deposit 5 is deposited on the wire electrode 1 as shown in FIG.
It has been observed that it adheres more to the rear of the body than to the front and sides of the body. On the other hand, the machining speed depends on the tension applied to the wire electrode 1 as shown in Figure 4, where the horizontal axis represents the applied tension T (g) and the vertical axis represents the machining speed F (mm/min).
It was found that there is an upward trend, and the higher the tension, the faster the machining speed becomes. That is, it is believed that as the tension increases, the vibration of the wire electrode 1 decreases, and therefore the size of the opposed micro-gap can be uniformly controlled and stable electric discharge can be repeated, thereby increasing the machining speed. [Problems to be Solved by the Invention] Now, when using conventional wire electrodes made of copper or brass, as described above, deposits 5 mainly composed of copper remain on the machined surface, which significantly impairs dimensional accuracy. In areas where the machining energy was high, this deposit 5 sometimes reached a thickness of about 10 to 100 μm.
When the machining energy was further increased, deposits 5 even filled the machining grooves 4 as shown in FIG. Due to such a phenomenon, not only does the workpiece not fall out, but also the machining fluid 3 jetted coaxially with the wire electrode 1 does not enter the minute gap at the opposing position, causing an air discharge phenomenon. However, the machining speed may be reduced and the wire electrode 1 may be broken. To remove these deposits 5, since the main component is copper, dangerous chemicals such as fuming nitric acid must be used, resulting in poor workability and safety issues. On the other hand, when it comes to increasing the processing speed, the wire electrode 1 made of copper or brass has a limit in its own tensile strength, and it is not possible to increase the processing speed by dramatically increasing the tension. Furthermore, wire electrodes made of tungsten or molybdenum have a high tensile strength, but due to their material nature they cannot be processed very quickly and are expensive. Furthermore, the conventional brass wire electrode 1 has the disadvantage of stress corrosion cracking and breakage when exposed to an atmosphere such as ammonia, so special care must be taken when storing it. It was necessary. As described above, the conventional wire electrode 1 has various drawbacks. This invention was made in view of the above-mentioned drawbacks, and provides a wire electrode for wire electrical discharge machining that has high tensile strength, stress corrosion resistance, is difficult to attract deposits, and enables high-speed, high-precision machining. This is what we provide. [Means for Solving the Problems] The wire cut wire electrode for electric discharge machining according to the present invention contains 0.1 to 1.5% by weight of iron, 3.0 to 6.0% by weight of tin, 0.01 to 0.06% by weight of phosphorus, and the balance being copper and unavoidable impurities. The surface of the main body is coated with a coating metal made of an alloy made by melting one metal or two or more selected from zinc, magnesium, tin, lead, aluminum, and cadmium. [Function] In the present invention, zinc, magnesium, tin, and lead are added to the surface of the main body consisting of 0.1 to 1.5% by weight of iron, 3.0 to 6.0% by weight of tin, 0.01 to 0.06% by weight of phosphorus, and the balance being copper and unavoidable impurities. , aluminum, and cadmium, or an alloy made by melting two or more of them. - Carried by a main body made of phosphorus-copper alloy,
In addition, adhesion of copper due to electric discharge is prevented by evaporating the coating metal with a low melting point and discharging discharge particles containing copper as a main component out of the machining groove together with the vaporized machining fluid. Table 1 shows the results of confirming the relationship between the amount of deposits 5 and the machining speed depending on the material of the wire electrode in wire cut electrical discharge machining. This result is a model of the electrode material of wire electrode 1 with a diameter of 3 mm and a length of
A 50 mm round bar was used as a test piece, and the conditions such as the pulse voltage applied to the opposing micro-gap and the machining fluid were the same. It is shown in

[Table] First, regarding the amount of adhesion, it can be seen that the lower the melting point and the smaller the latent heat of fusion and latent heat of vaporization of the material, the smaller the amount of adhesion. The workpiece 2 is heated to a molten state by the thermal energy during the discharge, and at the same time, the wire electrode 1 itself is also heated to the same extent. At this time, the machining fluid 3 vaporizes due to the rapid temperature rise,
A local explosion occurs, blowing away the molten part of the workpiece 2. The above situation is repeated, but among the materials constituting the electrode, the electrode material that has a low melting point and is easily evaporated is evaporated during discharge and is discharged to the outside of the machining groove 4 together with the vaporized machining fluid. In other words, the reason why an electrode material with a low melting point has a small amount of adhesion is because it scatters in a gaseous state and becomes difficult to adhere to the processed surface. On the other hand, copper, etc., which has a high melting point and is difficult to evaporate,
Even with the thermal energy of the discharge, most of the molten part does not evaporate, and when it becomes fine particles and scatters, it is welded to the machined surface, resulting in a large amount of adhesion. It was also confirmed that zinc and tin, which are low melting point metals, were good in processing speed. However, low melting point metals such as zinc and tin have low tensile strength as shown in Table 1, and the wire electrode 1
It is impossible to draw an electrode material having a diameter of 0.05 to 0.3 mm because wire breakage occurs frequently. Therefore, in the present invention, in order to improve the tensile strength,
A copper-iron-tin-phosphorus alloy was used as the electrode material for the wire electrode body. The preferred composition of this alloy is as follows. Including tin in copper improves mechanical properties such as tensile strength and hardness, but
If it exceeds 10%, it becomes practically impossible to cool with a good yield and it becomes expensive, so the tin content is preferably 3.0 to 6.0% by weight. When 0.01 to 0.5% of phosphorus is contained in a copper-tin alloy, the flow of the molten metal improves, and at the same time, the hardness and strength of the alloy are increased, and the wear resistance and elasticity are improved, but it is preferably 0.01 to 0.06%. A trace amount of % by weight is added. Adding iron improves high-temperature strength, but it reduces cold workability, so iron should be added to the copper alloy at a maximum of 2%.
It is difficult to add only a small amount. The preferred amount of iron added is
It is 0.5-1.5%. [Example] For the wire electrode body of the example of the present invention,
An alloy with a composition of 0.6% by weight of iron, 4.0% by weight of tin, 0.03% by weight of phosphorus, and the balance copper (contains 0.1% by weight of zinc as an unavoidable impurity) is cold drawn to a diameter of approximately 0.2 mm. A wire rod was prepared (hereinafter this wire rod is referred to as NBW). Since NBW itself is an alloy mainly composed of copper, when it is used for wire electrodes, the adhesion phenomenon is comparable to that of copper. Therefore, in order to solve this problem, 10μ of zinc was applied to the entire surface of the above NBW using the plating method.
The wire electrode according to the example was obtained by coating the wire to a thickness of m. A schematic cross section of this wire electrode is shown in FIG. 6 is the main body made of NBW, and 7 is the zinc coating. The characteristics of the wire electrode according to the present invention manufactured based on such a configuration and manufacturing method are compared with a conventional wire electrode using brass and copper as the electrode material and an NBW electrode material without a coating. Shown in the table. The characteristics in this table are based on the actual machining of copper material as a workpiece using a wire electrical discharge machine.The various machining conditions are standardized, and the characteristics are based on the characteristics when using brass wire electrodes. It is expressed as a percentage.

[Table] Among wire electrodes, those using bare NBW have a tensile strength that is 2.6 times that of copper wire electrodes, making it possible to increase the tension during actual processing and improve processing speed. Regarding the amount of copper-based alloy coating, bare
As mentioned above, the NBW wire electrode has a slightly lower melting point than the copper wire electrode due to the effect of tin, which has a low melting point. In the example of the present invention, the tensile strength was slightly higher than that of the brass wire electrode, and the amount of deposited copper alloy was small, so the processing speed was improved by 1.7 times. This result is close to the characteristic value when using a wire electrode made of zinc alone in the model experiment, confirming that it is advantageous to use a low melting point metal in actual wire electric discharge machining. It has been found that the reason why the wire electrode according to the present invention has good characteristics is that it has the same effect as the results of experiments using a model. In the above example, an alloy having a tensile strength higher than that of brass is used as the wire electrode body, and this is used as the core material to coat zinc. However, the coating metal is a metal that has a lower melting point and is more easily vaporized than the wire electrode body. or an alloy; in addition, tin,
One metal selected from lead, cadmium, magnesium, and aluminum, or an alloy formed by melting two or more of these metals can be used. [Effects of the Invention] As described above, the present invention has iron content of 0.1 to 1.5% by weight and 3.0% by weight of iron.
~6.0% by weight of tin, 0.01~0.06% by weight of phosphorus, and the balance being copper and unavoidable impurities. One or more metals selected from zinc, magnesium, tin, lead, aluminum, and cadmium are applied to the surface of the main body. Since it is coated with a coating metal made of a molten alloy, the main component is copper alloy wire, so it can have sufficient tensile strength, and the surface is coated with a low melting point metal, so It is possible to achieve both improved processing speed and prevention of adhesion of scattered electrode materials.
A wire electrode with good processing accuracy can be obtained.

[Brief explanation of drawings]

Figure 1 is a diagram showing the state of wire cut electric discharge machining, Figures 2 and 3 are diagrams showing the state of attachment of the electrode material of a conventional wire electrode to the workpiece surface, and Figure 4 is a diagram showing the state of attachment of the electrode material of a conventional wire electrode to the workpiece surface.
Diagram showing the relationship between wire electrode tension and processing speed,
FIG. 5 is a sectional view of a wire electrode showing the present invention. In the figure, 1 is a wire electrode, 2 is a workpiece, 3 is a machining liquid, 4 is a machining groove, 5 is a deposit, 6 is a wire electrode body according to the present invention, and 7 is a coated metal. Note that the same reference numerals in the figures represent the same parts.

Claims (1)

[Claims] 1 0.1-1.5% by weight iron, 3.0-6.0% by weight tin,
Zinc, magnesium,
A wire cut wire electrode for electrical discharge machining, which is coated with a coating metal made of an alloy made by melting one metal or two or more selected from tin, lead, aluminum, and cadmium.