Electrode wire for electrical discharge machining

Abstract

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

Description

Technical Field

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

Background Art

[0002] Wire electrical discharge machining is a machining method that cuts a workpiece by generating an electrical discharge phenomenon between an electrode wire for electrical discharge machining and the workpiece. Wire electrical discharge machining is suitable for manufacturing products having complex shapes such as molds. Electrode wires for electrical discharge machining are disclosed in Patent Documents 1 and 2. There is a demand for electrode wires for electrical discharge machining that enable high-speed electrical discharge machining and have excellent automatic connection properties. In recent years, there has been a demand for improving the dimensional accuracy and surface roughness of workpieces. As a material for the electrode wire for electrical discharge machining, brass, which is an alloy of copper and zinc, is used. Conventionally widely used brass is 65 / 35 brass having a composition of 65% by mass of Cu and 35% by mass of Zn. Research has been conducted to increase the machining speed compared to conventional electrode wires for electrical discharge machining, and one of them is to increase the zinc concentration in the brass composition. In addition, in order to enable high-speed electrical discharge machining, an electrode wire for electrical discharge machining having a composite structure in which an alloy layer having a higher zinc concentration is formed on the surface of the wire has also been proposed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, the manufacturing of large mold parts and other components by wire electrical discharge machining (EDM) has been increasing in technological fields such as automobiles and aircraft. When processing large mold parts and other components, there is a growing need among users to increase the processing speed. In one aspect of this disclosure, it is preferable to provide an EDM electrode wire that can increase the processing speed. [Means for solving the problem]

[0005] One aspect of this disclosure is an electrical discharge machining electrode wire having a copper mass ratio of 55.5% by mass or more and 58.5% by mass or less, a zinc mass ratio of 41.5% by mass or more and 44.5% by mass or less, a diameter of 0.395 mm or more and 0.45 mm or less, and a tensile strength of 900 MPa or more. This electrical discharge machining electrode wire, one aspect of this disclosure, can increase the machining speed. [Brief explanation of the drawing]

[0006] [Figure 1] This is a schematic diagram showing how a flat workpiece is processed using wire electrical discharge machining. [Figure 2] This is a cross-sectional view showing the orthogonal cross-section of an electrode wire used for electrical discharge machining. [Figure 3] This is an explanatory diagram illustrating a method for measuring the width W and the number of peaks M. [Figure 4] Figure 4A is an explanatory diagram showing the measurement locations for width on the sample piece. Figure 4B is an explanatory diagram showing the measurement locations for surface roughness on the sample piece. [Modes for carrying out the invention]

[0007] Exemplary embodiments of this disclosure will be described with reference to the drawings. 1. Configuration of the electrode wire 1 for electrical discharge machining As shown in Figure 1, the electrical discharge machining electrode wire 1 is a linear component. The orthogonal cross-section of the electrical discharge machining electrode wire 1 is circular, for example, as shown in Figure 2. An orthogonal cross-section is a cross-section perpendicular to the longitudinal direction of the electrical discharge machining electrode wire 1.

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

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

[0010] The diameter D of the electrical discharge machining electrode wire 1 shown in Figure 2 is between 0.395 mm and 0.45 mm. A diameter D of 0.395 mm to 0.45 mm allows a large current to flow through the electrical discharge machining electrode wire 1, resulting in a higher machining speed. 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 electrical discharge machining electrode wire 1 is 900 MPa or higher. This high tensile strength makes the electrode wire 1 less prone to breakage. Furthermore, it allows for greater tension to be applied to the electrode wire 1, resulting in higher machining speeds. The tensile strength is measured according to the JIS C3002 standard.

[0012] The straightness of the electrical discharge machining electrode wire 1 is indicated by the width W and the number of peaks M, as shown in Figure 3. The width W and the number of peaks M can be measured as follows: Prepare an electrical discharge machining electrode wire 1 with a length of 1 m or more. Fix one end of the electrical discharge machining electrode wire 1 and let the electrode wire 1 hang vertically. At this time, no tension is applied to the electrical discharge machining electrode wire 1.

[0013] A marking line 10 is attached to the electrical discharge machining electrode wire 1 at a point 1000 mm above the lower end 1A, which is the lower end of the electrical discharge machining electrode wire 1. The width W is the horizontal spread of the portion of the electrical discharge machining electrode wire 1 between the marking line 10 and the lower end 1A. The peak M is a portion of the electrical discharge machining electrode wire 1 that has a single peak-like shape and exists between the marking line 10 and the lower end 1A.

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

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

[0016] 2. Method for manufacturing electrode wire 1 for electrical discharge machining For example, an electrode wire 1 for electrical discharge machining can be manufactured by the following method. (a) A cast billet is manufactured. The composition of the cast billet is the same as the composition of the electrode wire 1 for electrical discharge machining. (b) Roughly drawn wire is produced by hot extrusion. (c) Heat treatment is applied to the roughly drawn wire. (d) After peeling, wire drawing and electric current heat treatment are performed. The electric current heat treatment is a process called low-temperature annealing. Also, peeling means removing the surface oxide layer. Through the processes up to this point, 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 it. The conditions for the electric current heat treatment are set such 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) The intermediate material T with a diameter A is wire-drawn to a diameter D to obtain an electrode wire. The degree of working Z(%) at this time is represented by the following formula (1). Formula (1) Z=(1 - D 2 / A 2 )×100 The greater the degree of working Z, the greater the tensile strength of the electric discharge machining electrode wire 1.

[0018] (f) Stress relief annealing is performed on the electrode wire. Stress relief annealing is a process of heat treatment by passing an electric current through the electrode wire. Through the processes up to this point, the electric discharge machining electrode wire 1 is completed. The higher the voltage V applied to the electrode wire in stress relief annealing, the better the straightness of the electric discharge machining electrode wire 1 and the smaller the tensile strength. For example, by setting the voltage V to 18 V or more and less than 20 V, the width W can be 80 mm or less, the number of peaks M can be 2 or less, and the tensile strength can be 900 MPa or more. (g) The electric discharge machining electrode wire 1 is rewound. Rewinding means rewinding from a large bobbin to a small bobbin.

[0019] 3. Effects of the electric discharge machining 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) By using the electric discharge machining electrode wire 1, the surface accuracy can be improved. For example, by using the electric discharge machining electrode wire 1, the surface roughness Ry on the machined surface can be reduced.

[0020] 4. Examples (1) Manufacturing of electrode wire S1 for electrical discharge machining The electrode wire S1 for electrical discharge machining was manufactured using the method described above. The mass ratio of copper in the cast billet was 57% by mass, and the mass ratio of zinc was 43% by 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 fracture. The tensile strength of the intermediate material T is preferably 550 MPa or higher, and more preferably 570 MPa or higher. The elongation of the intermediate material T is preferably 20% to 27%, and more preferably 20% to 25%. When the elongation of the intermediate material T is 20% or higher, the degree of processing Z is reduced, and the risk of wire breakage in step (e) is reduced. When the elongation of the intermediate material T is 27% or lower, the tensile strength of the electrical discharge machining electrode wire S1 is increased. By performing electrical heat treatment in step (d), the tensile strength of the electrical discharge machining electrode wire S1 can be increased while suppressing the risk of wire breakage in step (e). The degree of processing Z was 88.89%. The voltage V during strain relief annealing was 19V.

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

[0022] (2) Manufacturing of electrode wire S2 for electrical discharge machining The electrical discharge machining electrode wire S2 was manufactured using essentially the same method as the manufacturing method for the electrical discharge machining electrode wire S1. However, in the manufacturing of the electrical discharge machining electrode wire S2, the diameter A was 0.9 mm and the machining degree Z was 80.25%. The tensile strength of the electrical discharge machining electrode wire S2 was 872 MPa.

[0023] (3) Manufacturing of electrode wires S3 to S4 for electrical discharge machining Basically, the electrical discharge machining (EDM) electrode wires S3 and S4 were manufactured using the same method as the manufacturing method for the EDM electrode wire S1. However, the voltage V applied to the EDM electrode wire during strain relief annealing was 0V for EDM electrode wire S3 and 17V for EDM electrode wire S4. Some of the manufacturing conditions and characteristics of EDM electrode wires S1, S3, and S4 are shown in Table 1. In Table 1, "elongation" refers to elongation at fracture.

[0024] [Table 1]

[0025] (2) Evaluation of electrode wires for electrical discharge machining (2-1) Evaluation of processing speed Wire electrical discharge machining (EDM) was performed using electrode wire S1. The machining conditions were as follows:

[0026] Wire EDM machine model: U86-Makino Material and thickness of workpiece 2: Steel LPH62, 30mm thick A straight machining process was performed over a length of 22 mm. The machining speed was calculated from the time required for the straight machining and the length of 22 mm. The machining speed was 4.55 mm / min.

[0027] Furthermore, wire electrical discharge machining was performed in the same manner using electrical discharge machining electrode wire S2 instead of electrical discharge machining electrode wire S1, and the machining speed was calculated. The machining speed was 4.40 mm / min. Also, wire electrical discharge machining was performed in the same manner using commercially available electrical discharge machining electrode wire R instead of electrical discharge machining 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 electrical discharge machining was performed using the electrode wire S1 for electrical discharge machining, and the sample piece 11 shown in Figure 4A was cut from the workpiece 2. The basic shape of the sample piece 11 was a square plate in plan view. The target value for the length of one side of the square was 8.000 mm.

[0029] At positions Y1, Y2, and Y3 shown in Figure 4A, the width of the sample piece 11 in the Y direction was measured. The Y direction was perpendicular to the thickness direction of the sample piece 11 and perpendicular to two opposite sides of the square. The width measurement described above was performed at three locations in the thickness direction of the sample piece 11 at each of the Y1, Y2, and Y3 positions. These three locations are "top," "middle," and "bottom" as 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] In Table 2, "Error" refers to the difference from the target value of 8.000 mm. Table 2 shows the "Max," "Min," and "Difference" for Y1, Y2, and Y3, respectively. "Max" is the maximum value among the "Upper," "Middle," and "Lower" measurements. "Min" is the minimum value among the "Upper," "Middle," and "Lower" measurements. "Difference" is the value obtained by subtracting "Min" from "Max."

[0032] Furthermore, the width of the sample piece 11 in the X direction was measured at positions X1 and X2 shown in Figure 4A. The X direction was perpendicular to the thickness direction of the sample piece 11 and perpendicular to the Y direction. The width measurement described above was performed at three locations in the thickness direction of the sample piece 11 at each of the positions X1 and X2. These three locations are "top," "middle," and "bottom" as 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] In Table 3, "Error" refers to the difference from the target value of 8.000 mm. Table 3 shows the "Max," "Min," and "Difference" for X1 and X2, respectively. "Max" is the maximum value among the "Upper," "Middle," and "Lower" measurements. "Min" is the minimum value among the "Upper," "Middle," and "Lower" measurements. "Difference" is the value obtained by subtracting "Min" from "Max."

[0035] Furthermore, the same wire electrical discharge machining and measurements were 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 using the electrical discharge machining electrode wire S1 was smaller than the "difference" when using the electrical discharge machining electrode wire R. This result indicates that dimensional accuracy is higher when using the electrical discharge machining electrode wire S1.

[0036] (2-3) Evaluation of surface roughness Ry Wire electrical discharge machining was performed using the electrode wire S1 for electrical discharge machining, and a sample piece 11, shown in Figure 4B, was cut from the workpiece 2. The shape of the sample piece 11 was the same as the shape of the sample piece 11 in "(2-2) Evaluation of Dimensional Accuracy" above. As shown in Figure 4B, the three sides of the sample piece 11 were designated as sides 11A, 11B, and 11C. The surface roughness Ry was measured at the end face of each of the sides 11A, 11B, and 11C of the sample piece 11. 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 in the "top," "middle," and "bottom" directions in the thickness direction of the sample piece 11, as well as 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. "Wire running direction" refers to the vertical direction in Figure 1. The measurement results are shown in Table 4.

[0038] [Table 4]

[0039] Furthermore, the same wire electrical discharge machining and measurements were 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 using the electrical discharge machining electrode wire S1 was smaller than the surface roughness Ry when using the electrical discharge machining electrode wire R. This result indicates that the surface roughness Ry is smaller when using the electrical discharge machining electrode wire S1.

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

[0041] (1) The function of one component in each of the above embodiments may be divided among multiple components, or the function of multiple components may be performed by one component. Also, some of the configurations of each of the above embodiments may be omitted. Also, at least some of the configurations of each of the above embodiments may be added to, replaced with, etc., the configurations of other embodiments.

[0042] (2) In addition to the electrical discharge machining electrode wire 1 described above, this disclosure can also be realized in various forms, such as a system comprising the electrical discharge machining electrode wire 1, a method for manufacturing the electrical discharge machining electrode wire 1, and a wire electrical discharge machining method. [Explanation of Symbols]

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

Claims

1. The mass ratio of copper is 55.5% by mass or more and 58.5% by mass or less. The mass ratio of zinc is 41.5% by mass or more and 44.5% by mass or less. The diameter is between 0.395 mm and 0.45 mm. The tensile strength is 900 MPa or more. Electrode wire for electrical discharge machining.

2. An electrode wire for electrical discharge machining according to claim 1, When the electrical discharge machining electrode wire is suspended vertically, the horizontal width of the portion of the electrical discharge machining electrode wire within a range of 1 m from the lower end is 80 mm or less. Electrode wire for electrical discharge machining.

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