Electrode wire for electrical discharge machining

Abstract

To provide an electrode wire for electric discharge machining that can increase the machining speed. [Solution] In the electric discharge machining electrode wire, the mass ratio of copper is 55.5 mass% or more and 58.5 mass% or less, and the mass ratio of zinc is 41.5 mass% or more and 44.5 mass% or less. The diameter of the electric discharge machining electrode wire is 0.395 mm or more and 0.45 mm or less. The tensile strength of the electric discharge machining electrode wire is 900 MPa or more. For example, when the electric discharge machining electrode wire is hung vertically, the horizontal width of the portion of the electric discharge machining electrode wire within a range of 1 m from the bottom end is 80 mm or less.

Description

[Technical Field]

[0001] The present disclosure relates to an electrode wire for electrical discharge machining. [Background technology]

[0002] Wire EDM is a process that cuts a workpiece by generating an electric discharge between the electrode wire and the workpiece. Wire EDM is suitable for manufacturing products with complex shapes, such as molds. EDM electrode wires are disclosed in Patent Documents 1 and 2. EDM electrode wires are required to enable high-speed EDM and have excellent automatic wire threading capabilities. Recently, there has been a demand for improved dimensional accuracy and surface roughness of workpieces. Brass, an alloy of copper and zinc, is used as the material for EDM electrode wires. The most widely used brass is 65 / 35 brass, which has a composition of 65% Cu and 35% Zn by mass. Research is being conducted to increase the machining speed compared to conventional EDM electrode wires, including increasing the zinc concentration in the brass composition. Furthermore, composite EDM electrode wires have been proposed, in which a higher-zinc alloy layer is formed on the wire surface to enable high-speed EDM. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 9-11048 [Patent Document 2] Japanese Patent Application Laid-Open No. 2024-39167 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, in technical fields such as automobiles and aircraft, large mold parts and the like have increasingly been manufactured by wire electric discharge machining. When machining large mold parts and the like, there is a growing need among users to increase the machining speed. In one aspect of the present disclosure, it is preferable to provide an electric discharge machining electrode wire that can increase the machining speed. [Means for solving the problem]

[0005] One aspect of the present disclosure is an electric discharge machining electrode wire having a copper mass ratio of 55.5 mass % to 58.5 mass % and a zinc mass ratio of 41.5 mass % to 44.5 mass %, a diameter of 0.395 mm to 0.45 mm, and a tensile strength of 900 MPa or greater. The electric discharge machining electrode wire of one aspect of the present disclosure can increase the machining speed. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is a schematic diagram showing how a flat workpiece is machined by wire electric discharge machining. FIG. [Figure 2] FIG. 2 is a cross-sectional view showing an orthogonal cross section of an electric discharge machining electrode wire. [Figure 3] 10 is an explanatory diagram showing a method for measuring the width W and the number of ridges M. FIG. [Figure 4] 4A and 4B are explanatory diagrams showing the measurement positions of the width and surface roughness on the test piece, respectively. DETAILED DESCRIPTION OF THE INVENTION

[0007] Exemplary embodiments of the present disclosure will now be described with reference to the drawings. 1. Structure of the electrode wire for electrical discharge machining 1 As shown in Fig. 1, the electric discharge machining electrode wire 1 is a linear member. The orthogonal cross section of the electric discharge machining electrode wire 1 has a circular shape, for example, as shown in Fig. 2. The orthogonal cross section is a cross section perpendicular to the longitudinal direction of the electric discharge machining electrode wire 1.

[0008] The mass ratio of copper in the electric discharge machining electrode wire 1 is 55.5 mass% or more and 58.5 mass% or less. The mass ratio of zinc in the electric discharge machining electrode wire 1 is 41.5 mass% or more and 44.5 mass% or less. When the mass ratio of copper and the mass ratio of zinc are within the above ranges, the machining speed increases.

[0009] The mass ratio of copper in the electric discharge machining electrode wire 1 is preferably 56.5 mass% or more and 57.5 mass% or less, and more preferably 56.8 mass% or more and 57.2 mass% or less. The mass ratio of zinc in the electric discharge machining electrode wire 1 is preferably 42.5 mass% or more and 43.5 mass% or less, and more preferably 42.8 mass% or more and 43.2 mass% or less. The electric discharge machining electrode wire 1 may or may not further contain an element other than copper or zinc.

[0010] The diameter D of the electric discharge machining electrode wire 1 shown in Fig. 2 is 0.395 mm or more and 0.45 mm or less. By having the diameter D of 0.395 mm or more and 0.45 mm or less, a large current can be passed through the electric discharge machining electrode wire 1. As a result, the machining speed increases. The diameter D is preferably 0.44 mm or less, more preferably 0.43 mm or less, and particularly preferably 0.405 mm or less.

[0011] The tensile strength of the electric discharge machining electrode wire 1 is 900 MPa or more. Since the electric discharge machining electrode wire 1 has a tensile strength of 900 MPa or more, the electric discharge machining electrode wire 1 is less likely to break. In addition, a large tension can be applied to the electric discharge machining electrode wire 1. As a result, the machining speed increases. The tensile strength is measured according to JIS C3002.

[0012] The width W and the number of ridges M shown in FIG. 3 are indicators of the straightness of the electric discharge machining electrode wire 1. The width W and the number of ridges M can be measured as follows. An electric discharge machining electrode wire 1 having a length of 1 m or more is prepared. One end of the electric discharge machining electrode wire 1 is fixed, and the electric discharge machining electrode wire 1 is hung vertically. At this time, no tension is applied to the electric discharge machining electrode wire 1.

[0013] A marked line 10 is attached to a portion of the electric discharge machining electrode wire 1 that is 1000 mm above a lower end 1A, which is the lower end of the electric discharge machining electrode wire 1. The horizontal extent of the portion of the electric discharge machining electrode wire 1 between the marked line 10 and the lower end 1A is defined as width W. The peak M is a portion of the electric discharge machining electrode wire 1 that is present in the portion between the marked line 10 and the lower end 1A and has a mountain-like shape.

[0014] The smaller the width W, the higher the straightness of the electric discharge machining electrode wire 1. The fewer the number of ridges M, the higher the straightness of the electric discharge machining electrode wire 1. The width W is preferably 80 mm or less. The number of ridges M is preferably 2 or less. High straightness of the electric discharge machining electrode wire 1 improves automatic wire connection characteristics.

[0015] An electric discharge machining electrode wire 1 can be used as shown in FIG. 1. A machining power supply 3 applies a pulse voltage between the electric discharge machining electrode wire 1 and a workpiece 2 made of a metal material. At this time, an electric discharge occurs between the electric discharge machining electrode wire 1 and the workpiece 2. While the electric discharge is occurring, the electric discharge machining electrode wire 1 is moved relative to the workpiece 2. The electric discharge machining electrode wire 1 is also fed at a predetermined speed in the vertical direction in FIG. 1. As a result, two-dimensional machining can be performed on the workpiece 2. The workpiece 2 has a shape of, for example, a flat plate.

[0016] 2. Manufacturing method of the electrode wire for electric discharge machining 1 For example, the electric discharge machining electrode wire 1 can be manufactured by the following method. (a) A cast billet is produced. The composition of the cast billet is the same as the composition of the electrode wire 1 for electrical discharge machining. (b) A roughly drawn wire is produced by hot extrusion. (c) Heat treatment is performed on the roughly drawn wire. (d) After stripping, wire drawing and electrical heat treatment are performed. The electrical heat treatment is a process called low-temperature annealing. Also, stripping means removing the oxide layer on the surface. Through these processes, an intermediate material T with a diameter A is obtained. A is a value larger than D. A is, for example, 1.2 mm or a value close to that. The conditions for the electrical heat treatment are set so that the tensile strength of the intermediate material T is 550 MPa or more and the elongation is 20% or more and 27% or less.

[0017] (e) Intermediate material T with diameter A is drawn to have diameter D to form an electrode wire. The degree of processing Z (%) at this time is expressed by the following formula (1). Equation (1) Z=(1-D 2 / A 2 ) x 100 The greater the processing rate Z, the greater the tensile strength of the electric discharge machining electrode wire 1.

[0018] (f) The electrode wire is subjected to stress relief annealing. Strain relief annealing is a process in which the electrode wire is heat-treated by passing an electric current through it. Through these processes, the electric discharge machining electrode wire 1 is completed. The higher the voltage V applied to the electrode wire in stress relief annealing, the more improved the straightness of the electric discharge machining electrode wire 1 becomes and the lower the tensile strength becomes. For example, by setting the voltage V to 18 V or more but less than 20 V, the width W can be set to 80 mm or less, the number of ridges M to 2 or less, and the tensile strength to 900 MPa or more. (g) Rewinding the electric discharge machining electrode wire 1. Rewinding means rewinding from a large bobbin to a plastic bobbin.

[0019] 3. Effects of EDM electrode wire 1 (1A) The electric discharge machining electrode wire 1 has a high machining speed. (1B) The electric discharge machining electrode wire 1 has high straightness. (1C) Surface precision can be improved by using the electric discharge machining electrode wire 1. For example, by using the electric discharge machining electrode wire 1, the surface roughness Ry of the machined surface can be reduced.

[0020] 4. Working Example (1) Manufacturing of electrode wire S1 for electric discharge machining An electric discharge machining electrode wire S1 was manufactured using the method described above. The mass ratio of copper in the cast billet was 57 mass%, and the mass ratio of zinc was 43 mass%. The diameter A of the intermediate material T was 1.2±0.01 mm. The tensile strength of the intermediate material T was 592 MPa. The elongation of the intermediate material T was 26.4%. "Elongation" refers to the elongation at break. The tensile strength of the intermediate material T is preferably 550 MPa or more, and more preferably 570 MPa or more. The elongation of the intermediate material T is preferably 20% or more and 27% or less, and more preferably 20% or more and 25% or less. When the elongation of the intermediate material T is 20% or more, the degree of processing Z is low, and the risk of wire breakage in the step (e) is reduced. When the elongation of the intermediate material T is 27% or less, the tensile strength of the electric discharge machining electrode wire S1 is increased. By performing an electric current heat treatment in the step (d), the tensile strength of the electric discharge machining electrode wire S1 can be increased while reducing the risk of wire breakage in the step (e). The degree of processing Z was 88.89%. The voltage V in the stress relief annealing was 19 V.

[0021] The mass ratio of copper in the electric discharge machining electrode wire S1 was 57 mass %, and the mass ratio of zinc was 43 mass %. The diameter D was 0.4 mm. The tensile strength of the electric discharge machining electrode wire S1 was 937 MPa. The width W of the electric discharge machining electrode wire S1 was 80 mm, and the number of ridges M was 1.

[0022] (2) Manufacturing of electrode wire S2 for electric discharge machining The electric discharge machining electrode wire S2 was manufactured basically in the same manner as the electric discharge machining electrode wire S1. However, in manufacturing the electric discharge machining electrode wire S2, the diameter A was 0.9 mm and the processing rate Z was 80.25%. The electric discharge machining electrode wire S2 had a tensile strength of 872 MPa.

[0023] (3) Manufacturing of electrode wires S3 to S4 for electric discharge machining Electrical discharge machining electrode wires S3 to S4 were manufactured using a method basically similar to that of the electrical discharge machining electrode wire S1. However, the voltage V applied to the electrical discharge machining electrode wire during stress relief annealing was 0 V for the electrical discharge machining electrode wire S3 and 17 V for the electrical discharge machining electrode wire S4. Some of the manufacturing conditions and properties of the electrical discharge machining electrode wires S1 and S3 to S4 are shown in Table 1. Note that "elongation" in Table 1 refers to elongation at break.

[0024] [Table 1]

[0025] (2) Evaluation of electrode wire for electrical discharge machining (2-1) Evaluation of processing speed Wire electric discharge machining was carried out using the electric discharge machining electrode wire S1 under the following machining conditions.

[0026] Wire EDM model: U86-Makino Material and thickness of workpiece 2: Steel LPH62, 30 mm thick The straightening was carried out over a length of 22 mm. The processing speed was calculated from the time required for straightening and 22 mm. The processing speed was 4.55 mm / min.

[0027] Wire EDM was also performed in the same manner, using EDM electrode wire S2 instead of EDM electrode wire S1, and the machining speed was calculated. The machining speed was 4.40 mm / min. Wire EDM was also performed in the same manner, using commercially available EDM electrode wire R instead of EDM electrode wire S1, and the machining speed was calculated. The machining speed was 4.11 mm / min.

[0028] (2-2) Evaluation of dimensional accuracy Wire electric discharge machining was performed using an electric discharge machining electrode wire S1, and a sample piece 11 shown in FIG. 4A was cut out from the workpiece 2. The basic shape of the sample piece 11 was a square plate in plan view. The target length of one side of the square was 8,000 mm.

[0029] The width of the sample piece 11 in the Y direction was measured at positions Y1, Y2, and Y3 shown in FIG. 4A. The Y direction was perpendicular to the thickness direction of the sample piece 11 and perpendicular to two opposing sides of the square. The width measurements were also performed at three positions in the thickness direction of the sample piece 11 at positions Y1, Y2, and Y3. The three positions are "top," "middle," and "bottom" shown in Table 2. "Middle" is the center in the thickness direction. "Top" is a position closer to one main surface of the sample piece 11 than "middle." "Bottom" is a position closer to the opposite main surface of the sample piece 11 than "middle." The measurement results are shown in Table 2.

[0030] [Table 2]

[0031] "Error" in Table 2 is the difference from the target value of 8,000 mm. Table 2 shows "Max," "Min," and "Difference" for each of Y1, Y2, and Y3. "Max" is the maximum value among the measured values of "Top," "Mid," and "Bottom." "Min" is the minimum value among the measured values of "Top," "Mid," and "Bottom." "Difference" is the value obtained by subtracting "Min" from "Max."

[0032] The width of the sample piece 11 in the X direction was measured at positions X1 and X2 shown in FIG. 4A. The X direction was perpendicular to the thickness direction of the sample piece 11 and perpendicular to the Y direction. The width measurements were also performed at three positions in the thickness direction of the sample piece 11 at each of positions X1 and X2. The three positions are "top," "middle," and "bottom" shown in Table 3. "Middle" is the center in the thickness direction. "Top" is a position closer to one main surface of the sample piece 11 than "middle." "Bottom" is a position closer to the opposite main surface of the sample piece 11 than "middle." The measurement results are shown in Table 3.

[0033] [Table 3]

[0034] "Error" in Table 3 is the difference from the target value of 8,000 mm. Table 3 shows "Max," "Min," and "Difference" for each of X1 and X2. "Max" is the maximum value among the measured values of "Top," "Mid," and "Bottom." "Min" is the minimum value among the measured values of "Top," "Mid," and "Bottom." "Difference" is the value obtained by subtracting "Min" from "Max."

[0035] Similar wire electrical discharge machining and measurements were also performed using a commercially available electrical discharge machining electrode wire R instead of the electrical discharge machining electrode wire S1. The results are shown in Tables 2 and 3. As shown in Tables 2 and 3, the "difference" when the electrical discharge machining electrode wire S1 was used was smaller than the "difference" when the electrical discharge machining electrode wire R was used. This result indicates that the dimensional accuracy was higher when the electrical discharge machining electrode wire S1 was used.

[0036] (2-3) Evaluation of surface roughness Ry Wire electrical discharge machining was performed using an electrical discharge machining electrode wire S1, and a sample piece 11 shown in FIG. 4B was cut out from the workpiece 2. The shape of the sample piece 11 was the same as that of the sample piece 11 in "(2-2) Evaluation of Dimensional Accuracy" above. As shown in FIG. 4B, the three sides of the sample piece 11 were designated as sides 11A, 11B, and 11C, respectively. The surface roughness Ry of the end face of the sample piece 11 was measured for each of sides 11A, 11B, and 11C. The surface roughness Ry corresponds to Rz in JIS B 0601:2001. A Surfcorder SE3500 manufactured by Kosaka Laboratory was used to measure the surface roughness Ry.

[0037] Furthermore, the surface roughness Ry was measured for each of the sides 11A, 11B, and 11C at the "top," "middle," and "bottom" in the thickness direction of the test piece 11, and in the "wire running direction." The meanings of "top," "middle," and "bottom" are the same as those of "top," "middle," and "bottom" in "(2-2) Evaluation of dimensional accuracy" above. The "wire running direction" refers to the up-down direction in Figure 1. The measurement results are shown in Table 4.

[0038] [Table 4]

[0039] Similar wire electrical discharge machining and measurements were also performed using a commercially available electrical discharge machining electrode wire R instead of the electrical discharge machining electrode wire S1. The results are shown in Table 4. As shown in Table 4, the surface roughness Ry when the electrical discharge machining electrode wire S1 was used was smaller than the surface roughness Ry when the electrical discharge machining electrode wire R was used. This result indicates that the surface roughness Ry is smaller when the electrical discharge machining electrode wire S1 is used.

[0040] 5. Other Embodiments Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms.

[0041] (1) The function of one component in each of the above embodiments may be shared among multiple components, or the functions of multiple components may be performed by one component. Also, part of the configuration of each of the above embodiments may be omitted. Furthermore, at least part of the configuration of each of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0042] (2) In addition to the above-described electric discharge machining electrode wire 1, the present disclosure can also be realized in various forms, such as a system including the electric discharge machining electrode wire 1 as a component, a manufacturing method for the electric discharge machining electrode wire 1, and a wire electric discharge machining method. [Explanation of symbols]

[0043] 1...Electrode wire for electrical discharge machining, 1A...lower end, 2...workpiece, 3...machining power supply, 10...marked line, 11...sample piece, 11A, 11B, 11C...side, M...crest, W...width

Claims

1. The mass ratio of copper is 56.5 mass% or more and 57.5 mass% or less, The mass ratio of zinc is 42.5 mass% or more and 43.5 mass% or less, The diameter is 0.395 mm or more and 0.45 mm or less, An electric discharge machining electrode wire having a tensile strength of 900 MPa or more, When the electric discharge machining electrode wire is hung vertically, the horizontal width of a portion of the electric discharge machining electrode wire within a range of 1 m from the bottom end is 80 mm or less. Electrode wire for electrical discharge machining.

2. The electric discharge machining electrode wire according to claim 1, When the electric discharge machining electrode wire is hung vertically, the number of portions of the electric discharge machining electrode wire that have one mountain shape and are present in a range of 1 m from the bottom end is 2 or less. Electrode wire for electrical discharge machining.

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