Special-shaped die

Abstract

The cross-section of the bearing orthogonal to the wire drawing direction has a pair of long sides with relatively long side lengths and a pair of short sides with relatively short side lengths. In the cross-section of the reduction on the long side parallel to the wire drawing direction, the absolute value of the difference between the first reduction angle with respect to the wire drawing direction and the second reduction angle opposite to the first reduction angle is 2° or less. In the cross-section of the reduction on the short side parallel to the wire drawing direction, the absolute value of the difference between the third reduction angle with respect to the wire drawing direction and the fourth reduction angle opposite to the third reduction angle is 2° or less. The average value of the first reduction angle and the second reduction angle is larger than the average value of the third reduction angle and the fourth reduction angle.

Description

Technical Field

[0001] The present disclosure relates to a shaped die. This application claims priority based on Japanese Patent Application No. 2024-010950, filed on January 29, 2024. All the descriptions contained in the Japanese patent application are incorporated herein by reference.

Background Art

[0002] The shaped die is disclosed, for example, in International Publication No. 2018 / 123513.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

[0004] The shaped die of the present disclosure is a shaped die having a reduction on the upstream side in the wire drawing direction and a bearing having the smallest diameter adjacent to the reduction. The cross-section of the bearing perpendicular to the wire drawing direction has a pair of long sides with relatively long side lengths and a pair of short sides with relatively short side lengths. In the cross-section of the reduction parallel to the wire drawing direction and intersecting the long side, the absolute value of the difference between the first reduction angle with respect to the wire drawing direction and the second reduction angle opposite to the first reduction angle is 2° or less. In the cross-section of the reduction parallel to the wire drawing direction and intersecting the short side, the absolute value of the difference between the third reduction angle with respect to the wire drawing direction and the fourth reduction angle opposite to the third reduction angle is 2° or less. The average value of the first reduction angle and the second reduction angle is larger than the average value of the third reduction angle and the fourth reduction angle.

Brief Description of the Drawings

[0005]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0006] [Problems to be Solved by the Present Disclosure] In conventional irregular dies, it has been difficult to draw flat-shaped drawn wires.

[0007] [Description of Embodiments of the Present Disclosure] First, embodiments of the present disclosure will be listed and described.

[0008] Irregular wires having a square or similar cross-sectional shape are frequently used for motor coils and the like. In recent years, due to the spread of hybrid vehicles and electric vehicles, the demand for irregular wires has been increasing.

[0009] The irregular wires used for these are required to have a uniform wire diameter, no wire curl, and no scratches on the wire surface.

[0010] Scratches and defects on the wire surface may reduce the insulation of the coating applied after wire drawing. In such wire drawing of a wire with a special cross-section, a wire rod with a round cross-section is passed through a plurality of special-shaped dies, and the cross-sectional shape is sequentially plastically deformed into a special shape such as a square to obtain a special-shaped wire with a desired shape.

[0011] Among special-shaped dies, some have the same side length for each side, but the vast majority have different side lengths, and it is not easy to plastically deform each side uniformly in the same manner. In particular, for a special-shaped die with different side lengths having a long side and a short side, since the cross-sectional shape is deformed by each special-shaped die as described above, there is a problem that the stress applied to the incoming metal wire is less likely to be uniformly applied compared to a round die. As a result, differences occur in the contact distance between the wire and the inner surface of the die hole and the load during wire drawing depending on the part of the inner surface of the die hole, and wire kinks (curls) and scratches are likely to occur on the wire surface.

[0012] The special-shaped die of the present disclosure is a special-shaped die having a reduction on the upstream side in the wire drawing direction and a bearing with the smallest diameter adjacent to the reduction. The cross-section of the bearing orthogonal to the wire drawing direction has a pair of long sides with relatively long side lengths and a pair of short sides with relatively short side lengths. In the cross-section of the reduction that is parallel to the wire drawing direction and intersects the long side, the absolute value of the difference between the first reduction angle with respect to the wire drawing direction and the second reduction angle opposing the first reduction angle is 2° or less. In the cross-section of the reduction that is parallel to the wire drawing direction and intersects the short side, the absolute value of the difference between the third reduction angle with respect to the wire drawing direction and the fourth reduction angle opposing the third reduction angle is 2° or less. The average value of the first reduction angle and the second reduction angle is larger than the average value of the third reduction angle and the fourth reduction angle.

[0013] In the special-shaped die configured as described above, since the average value of the first reduction angle and the second reduction angle on the long side is larger than the average value of the third reduction angle and the fourth reduction angle on the short side, the reduction angle is adjusted according to the shape of the wire entering the reduction. As a result, it is possible to prevent scratches from occurring on the surface of the wire.

[0014] Preferably, the ratio (D2 / D1) of the length D2 of the short side to the length D1 of the long side is 1 / 11 or more and 4 / 5 or less. Within this range, high-quality deformed wires can be manufactured most effectively. More preferably, D2 / D1 is 1 / 10 or more and 4 / 5 or less.

[0015] Preferably, the first reduction angle and the second reduction angle are 5° or more and 20° or less.

[0016] Preferably, the length D2 of the short side is 10 μm or more and 10 mm or less. Preferably, the shaped die contains polycrystalline diamond.

[0017] Preferably, the absolute value of the difference between the first reduction angle and the second reduction angle is 0.5° or less, and the absolute value of the difference between the third reduction angle and the fourth reduction angle is 0.5° or less. It is preferable that the absolute value of the difference between the first and second reduction angles and the absolute value of the difference between the third and fourth reduction angles are small. However, setting the absolute value of the difference to 0 is costly. If this difference is 0.5° or less, high-quality deformed wires similar to those with a difference of 0° can be manufactured.

[0018] (Outline of the structure) The outline of a diamond die for drawing deformed wires will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a shaped diamond die 10 according to an embodiment, a diamond 1 constituting the shaped diamond die 10, a case 2 for housing the diamond 1, and a sintered alloy 3 interposed therebetween. FIG. 1 is a cross-sectional view of a state in which it can be used when housed in a die case. The diamond 1 is housed in the case 2. The diamond 1 is attached to the case 2 using the sintered alloy 3. In the shaped diamond die 10 as a shaped die, the portion for processing the wire is constituted by, for example, the diamond 1.

[0019] Figure 2 is a front view of the diamond 1 in Figure 1. Figure 3 is a cross-sectional view taken along line III-III in Figure 2. Figure 4 is a cross-sectional view taken along line IV-IV in Figure 2.

[0020] As shown in Figures 2 to 4, the diamond 1 has a polycrystalline diamond 5 surrounded by a cemented carbide support ring 4. And the central part is composed of an inner surface 6 of a hole through which the wire to be drawn passes while making contact and a machining hole 7. The inner surface 6 of the hole is further subdivided, and its details are shown in Figure 3. The inner surface 6 of the hole is successively divided into a bell 6a, an approach 6b, a reduction 6c, a bearing 6d, a back relief 6e, and an exit 6f. As shown in Figure 2, the shape seen from the front is similar to a quadrilateral. The bearing 6d is a region including the portion with the smallest diameter in the machining hole 7.

[0021] The diamond 1 is a polycrystalline diamond substantially composed of only diamond, that is, a diamond 1 without a so-called binder. As an example of a typical one, there is a diamond produced by directly converting non-diamond carbon into diamond under ultra-high pressure and high temperature, which is known as a binderless diamond.

[0022] The diamond 1 is not limited to a binderless diamond, and may be a diamond 1 having a binder. Further, the diamond 1 may contain an unconverted carbon component. Further, the diamond 1 may be replaced with a hard material such as cemented carbide or cubic boron nitride.

[0023] At least the surface from the bell 6a to the bearing 6d of the inner surface 6 of the hole formed by the machining hole 7 is formed as a smooth curved surface in the thickness direction of the diamond. That is, each of the bell 6a, the approach 6b, the reduction 6c, and the bearing 6d is not formed linearly and is different from the case where a roundness is provided at each boundary portion, and the entire portion is formed as a smooth curved surface. This curved surface is formed as a single R curved surface or a composite R curved surface, and the boundary portions between them have an unclear shape.

[0024] The wire diameter of the wire after wire drawing by the shaped diamond die 10 is, for example, less than 0.5 mm, which is a thin wire diameter. When drawing such a thin wire, if the surface from the bell 6a to the bearing 6d is formed as a smooth curved surface, there will be no significant change in the wire drawing resistance, and even for an extremely thin wire, it is difficult to break. Also, in terms of supplying the lubricant, if it is formed as a smooth curve, the lubrication conditions will be good.

[0025] The polycrystalline diamond 5 around the processing hole 7 is a single polycrystalline diamond continuous in the circumferential direction of the processing hole 7. Since the polycrystalline diamond 5 around the processing hole 7 is a single polycrystalline diamond continuous in the circumferential direction of the processing hole, it has high strength compared to the divided diamond. As a result, the accuracy of the processing hole is high, and the surface roughness of the wire after wire drawing can be reduced.

[0026] The pair of long sides 71, 72 of the bearing 6d face each other. The pair of short sides 73, 74 of the bearing 6d face each other. The length D1 of the long sides 71, 72 is the distance between the opposing short sides 73, 74. The length D2 of the short sides 73, 74 is the distance between the opposing long sides 71, 72.

[0027] The corners where the long sides 71, 72 and the short sides 73, 74 intersect may or may not be rounded.

[0028] (Method for specifying the shape of the die hole 7) To measure and specify the shapes of the bell 6a, approach 6b, reduction 6c, bearing 6d, back relief 6e, and exit 6f, the die hole 7 is filled with a transfer material (for example, Repliset manufactured by Stollas Co., Ltd.). Thereby, a replica transferring the shape of the die hole 7 is produced. Using a tool microscope with transmitted illumination, this replica is used to clarify the contour of the die hole 7, and cross-sectional views of the die hole 7 such as those of the die hole 7 in FIGS. 3 and 4 are obtained.

[0029] In the cross-sectional view, the part with the narrowest inner diameter and in a cylindrical shape is defined as bearing 6d. Let the distance between the short sides 73 and 74 of bearing 6d be D1. In the cross-sectional view, a part that is adjacent to bearing 6d and located upstream of bearing 6d, and whose inner dimension RD (parallel to D1) on the long side satisfies D1 < RD ≦ 1.500D1, is defined as reduction 6c. In the cross-sectional view, a part that is adjacent to bearing 6d and located downstream of bearing 6d, and whose inner dimension BD (parallel to D1) on the long side satisfies D1 < BD ≦ 1.100D1, is defined as back relief 6e.

[0030] When measuring the reduction angles C and D on the short side 73, 74 side of Figure 3, in the cross-sectional view of the die hole 7, draw tangent lines 103 and 104 on both side surfaces in the reference region (the part where RD = 1.500D1) of reduction 6c. Let the angle formed by tangent line 103 and the axis 100 be the reduction angle C. Let the angle formed by tangent line 104 and the axis 100 be the reduction angle D.

[0031] When measuring the reduction angles A and B on the long side 71, 72 side of Figure 4, in the cross-sectional view of the die hole 7, draw tangent lines 101 and 102 on both side surfaces in the above-mentioned reference region (the part where RD = 1.500D1) of reduction 6c. Let the angle formed by tangent line 101 and the axis 100 be the reduction angle A. Let the angle formed by tangent line 102 and the axis 100 be the reduction angle B.

[0032] (Radius of the corner part Radius R) Figure 5 is an enlarged cross-sectional view showing bearing 6d along the V-V line in Figure 3. Figure 6 is a cross-section corresponding to Figure 5, showing the corner part 7a1 and non-corner part 7b1 in reduction 6c.

[0033] The drawn wire is used for motor windings and the like. In such applications, since it is necessary to wind at a high density, the smaller the radius R of the corner part of the wire, the more preferable.

[0034] Therefore, the radii R and R1 of the square corner parts 7a and 7a1 of bearing 6d and reduction 6c are preferably small.

[0035] Reducing the angular difference of the reduction 6c on the opposing surfaces of the die holes 7 reduces the difference in the contact angle with the wire rod. Therefore, the difference in the wire drawing resistance is also reduced, and the difference in the stress applied to the wire rod between the opposing surfaces of the holes is reduced, making it less likely for the wire rod to curl.

[0036]

[0035] Also, if the reduction angle of the long sides 71, 72 where the wire rod contact surface is large is made larger than the reduction angle of the short sides 73, 74, the shape of the wire rod after wire drawing can be made closer to the target cross-sectional shape of the wire rod. As a result, when the wire rod contacts the next die, the timing at which the wire rod starts to contact the reduction 6c at the long sides 71, 72 and the short sides 73, 74 approaches. As a result, the difference in the axial wire rod contact distance on each side is reduced, the stress difference applied to the wire rod is reduced, and the occurrence of wire scratches can be reduced.

[0037] The wire rod to be wire drawn can be made of various metals such as copper, silver, iron, gold, and aluminum.

[0038] The shaped diamond die 10 as a shaped die has a reduction 6c and a bearing 6d with the smallest diameter adjacent to the reduction 6c from the upstream side in the wire drawing direction indicated by the arrow 110. The cross-section of the bearing 6d (Figure 2) perpendicular to the wire drawing direction has a pair of long sides 71, 72 with relatively long side lengths and a pair of short sides 73, 74 with relatively short side lengths.

[0039]

[0036] In the cross-section of the reduction 6c (Figure 4) parallel to the wire drawing direction and intersecting the long sides 71, 72, the absolute value of the difference between the first reduction angle A with respect to the wire drawing direction and the second reduction angle B opposing the first reduction angle A is 2° or less.

[0040] Parallel to the wire drawing direction and intersecting the short sides 73, 74 Bearing In the cross-section of 6d (Figure 3), the absolute value of the difference between the third reduction angle C with respect to the wire drawing direction and the fourth reduction angle D opposing the third reduction angle C is 2° or less.

[0041] The average value of the first reduction angle A and the second reduction angle B is greater than the average value of the third reduction angle C and the fourth reduction angle D.

[0042] [Details of Embodiments of the Present Disclosure] (Examples) (Test Specimen Numbers 1 to 8)

[0043] [Table 1]

[0044] Irregular diamond dies with test specimen numbers 1 to 8, in which various numerical values were set in various ways, were prepared.

[0045] The irregular diamond dies with test specimen numbers 1 to 8 were produced by the following method. First, a pilot hole was drilled in polycrystalline diamond by a laser processing method, and then rough machining was performed by an electrical discharge machining method. Next, finish machining was performed by a lapping process.

[0046] A square wire with a cross-sectional dimension of 550 μm × 550 μm and a material of copper was drawn in a lubricant (drawing speed: 10 m / min) for 1 hour to obtain a square wire with a length of 600 m. A 1-m sample (a sample near the rear end of the 600-m wire) was extracted from the square wire after 1 hour of drawing, and wire scratches and curl were evaluated. The results are shown in Table 1.

[0047] Regarding the evaluation of wire scratches, the surface of the square wire was observed with a microscope. Those with a scratch depth of less than 10 μm or no scratches were rated as "A", those with a scratch depth of 10 μm or more and less than 20 μm were rated as "B", and those with a scratch depth of 20 μm or more were rated as "C". Evaluations A and B were considered passing, and evaluation C was considered failing.

[0048] FIG. 7 is a diagram for explaining a method for measuring the curl of the wire 201. The wire 201, which is a square wire, is suspended vertically downward from the fixing portion 200. If the wire 201 is in a straight shape, the wire 201 exists at the position indicated by the dotted line. When the wire 201 is suspended from the fixing portion 200 and no force is applied to the wire 201, the wire 201 curls. As a result, the lower end 201e of the wire 201 moves upward by a vertical distance X from the position indicated by the dotted line. Regarding the evaluation of curl, assuming the length of the wire 201 is 1 m, if the distance X is 5 cm or less, it is rated as "A", if the distance X exceeds 5 cm and is 10 cm or less, it is rated as "B", and if the distance X exceeds 10 cm, it is rated as "C". Evaluations A and B are considered passing, and evaluation C is considered failing.

[0049] (Test Specimen Nos. 11 to 18)

[0050]

Table 2

[0051] Irregular diamond dies 10 of test specimen numbers 11 to 18 were fabricated. The irregular diamond die 10 has the structure shown in FIGS. 1 to 6. The length D1 of the long sides 71, 72 was 500 μm, the length D2 of the short sides 73, 74 was 200 μm, and the radius R of the corner portion 7a was 30 μm.

[0052] First, a pilot hole was drilled in the polycrystalline diamond by a laser processing method, and then rough machining was performed by an electrical discharge machining method. Next, finish machining was performed by lapping. In the process, for test specimen numbers 11 to 18, the reduction angles A to D with respect to the axis (FIGS. 3 and 4) were variously changed.

[0053] A square wire with a cross-sectional dimension of 550 μm × 550 μm and a material of copper was drawn in a lubricant (drawing speed: 10 m / min) for 1 hour to obtain a square wire with a length of 600 m. A 1-m long sample (a sample near the end of the 600-m wire) was extracted from the square wire after 1 hour of drawing, and wire scratches and curl were evaluated in the same manner as in Table 1. The results are shown in Table 2.

[0054] From Table 2, when the angular variation |A - B| is less than or equal to the angular variation |C - D|, it was found that the evaluation of "C" is obtained for linear scratches and curling. Any of

[0055] (Test Specimen Numbers 21 to 32)

[0056]

Table 3

[0057] Irregular diamond dies 10 with test specimen numbers from 21 to 32 were fabricated. The irregular diamond dies 10 have the structures shown in FIGS. 1 to 6. The lengths D1 of the long sides 71 and 72 were 500 μm, the lengths D2 of the short sides 73 and 74 were 200 μm, and the radius R of the corner portion 7a was 30 μm.

[0058] First, a pilot hole was drilled in polycrystalline diamond by a laser processing method, and then rough machining was performed by an electrical discharge machining method. Next, finish machining was performed by lapping. In the process, the reduction angles A to D with respect to the axis (FIGS. 3 and 4) were variously changed for test specimen numbers 21 to 32.

[0059] A square wire with a cross-sectional dimension of 550 μm × 550 μm and a material of copper was drawn in a lubricant (drawing speed: 10 m / min) for 1 hour to obtain a square wire with a length of 600 m. A 1-m sample (a sample near the rear end of the 600-m wire) was extracted from the square wire after 1 hour of drawing, and linear scratches and curling were evaluated in the same manner as in Table 1. The results are shown in Table 3.

[0060] From Table 3, it was found that when either the angular variation |A - B| or the angular variation |C - D| is 3° or more, an evaluation of "C" is obtained for either linear scratches or curling.

[0061] It was found that when the average value of the reduction angles A and B is larger than the average value of the reduction angles C and B, an evaluation of "B" or higher is obtained in the evaluation of linear scratches and curling. ​

[0062] It was found that if the sum of the angular variation |A - B| and the angular variation |C - D| is 3° or less, an evaluation of "A" can be obtained in the evaluation of linear scratches and curl.

[0063] (Test piece numbers 41 to 52)

[0064]

Table 4

[0065] Irregular diamond dies 10 with test piece numbers from 41 to 52 were created. The irregular diamond dies 10 have the structures shown in FIGS. 1 to 6. The length D1 of the long sides 71 and 72 was 500 μm, the length D2 of the short sides 73 and 74 was 400 μm, and the radius R of the corner part 7a was 30 μm.

[0066] First, a pilot hole was drilled in polycrystalline diamond by a laser processing method, and then rough machining was performed by an electrical discharge machining method. Next, finish machining was performed by lapping. In the process, the reduction angles A to D with respect to the axis (in FIGS. 3 and 4) were variously changed for test piece numbers 41 to 52.

[0067] A square wire with a cross-sectional dimension of 550 μm × 550 μm and a material of copper was drawn in a lubricant (drawing speed: 10 m / min) for 1 hour to obtain a square wire with a length of 600 m. A 1-m sample (a sample near the end of the 600-m wire) was extracted from the square wire after 1 hour of drawing, and linear scratches and curl were evaluated in the same manner as in Table 1. The results are shown in Table 4.

[0068] From Table 4, it was found that when either the angular variation |A - B| or the angular variation |C - D| is 3° or more, an evaluation of "C" is given in either linear scratches or curl.

[0069] It was found that if the average value of the reduction angles A and B is larger than the average value of the reduction angles C and B, an evaluation of "B" or higher can be obtained in the evaluation of linear scratches and curl.

[0070] It was found that if the total of the angular variation |A - B| and the angular variation |C - D| is 3° or less, an evaluation of "A" can be obtained in the evaluation of linear scratches and curling.

[0071] (Test piece numbers 61 to 72)

[0072] [Table 5]

[0073] Irregular diamond dies 10 with test piece numbers 61 to 72 were created. The irregular diamond dies 10 have the structures shown in FIGS. 1 to 6. The length D1 of the long sides 71 and 72 was 700 μm, the length D2 of the short sides 73 and 74 was 100 μm, and the radius R of the corner portion 7a was 30 μm.

[0074] First, a pilot hole was drilled in polycrystalline diamond by a laser processing method, and then rough machining was performed by an electrical discharge machining method. Next, finish machining was performed by lapping. In that process, the reduction angles A to D with respect to the axis (in FIGS. 3 and 4) were variously changed for test piece numbers 61 to 72.

[0075] A square wire with a cross-sectional dimension of 900 μm × 150 μm and a material of copper was drawn in a lubricant (drawing speed: 10 m / min) for 1 hour to obtain a square wire with a length of 600 m. A 1-m sample (a sample near the rear end of the 600-m wire) was extracted from the square wire after 1 hour of drawing, and linear scratches and curling were evaluated in the same manner as in Table 1. The results are shown in Table 5.

[0076] From Table 5, it was found that when either the angular variation |A - B| or the angular variation |C - D| is 3° or more, an evaluation of "C" is given in either linear scratches or curling.

[0077] It was found that if the average value of the reduction angles A and B is larger than the average value of the reduction angles C and B, an evaluation of "B" or higher can be obtained in the evaluation of linear scratches and curling.

[0078] It was found that if the total of the angular variation |A - B| and the angular variation |C - D| is 3° or less, an evaluation of "A" can be obtained in the evaluation of linear scratches and curl.

[0079] (Test Specimen Nos. 81 to 92)

[0080]

Table 6

[0081] Irregular diamond dies 10 with test specimen numbers from 81 to 92 were created. The irregular diamond dies 10 have the structures shown in FIGS. 1 to 6. The length D1 of the long sides 71, 72 was 1000 μm, the length D2 of the short sides 73, 74 was 100 μm, and the radius R of the corner portion 7a was 30 μm.

[0082] First, a pilot hole was drilled in polycrystalline diamond by a laser processing method, and then rough machining was performed by an electrical discharge machining method. Next, finish machining was performed by lapping. In that process, for test specimen numbers 61 to 72, the reduction angles A to D with respect to the axis (FIGS. 3 and 4) were variously changed.

[0083] A square wire with a cross-sectional dimension of 1200 μm × 150 μm and a material of copper was drawn in a lubricant (drawing speed: 10 m / min) for 1 hour to obtain a square wire with a length of 600 m. A 1-m sample (a sample near the end of the 600-m wire) was extracted from the square wire after 1 hour of drawing, and linear scratches and curl were evaluated in the same manner as in Table 1. The results are shown in Table 6.

[0084] From Table 6, it was found that when either the angular variation |A - B| or the angular variation |C - D| is 3° or more, an evaluation of "C" is given for either linear scratches or curl.

[0085] When the average values of the reduction angles A and B are greater than the average values of the reduction angles C and B, it was found that an evaluation of "B" or higher can be obtained in the evaluation of linear scratches and curls.

[0086] If the sum of the angle variations |A - B| and |C - D| is 3° or less, it was found that an evaluation of "A" can be obtained in the evaluation of linear scratches and curls.

[0087] (Test Specimen Numbers 101 to 112)

[0088]

Table 7

[0089] Irregular diamond dies 10 with test specimen numbers 101 to 112 were created. The irregular diamond dies 10 have the structure shown in FIGS. 1 to 6. The length D1 of the long sides 71, 72 was 1100 μm, the length D2 of the short sides 73, 74 was 100 μm, and the radius R of the corner portion 7a was 30 μm.

[0090] First, a pilot hole was drilled in the polycrystalline diamond by a laser processing method, and then rough machining was performed by an electrical discharge machining method. Next, finish machining was performed by lapping. In that process, the test specimen 101 from 112 to

[0091] The square wire with a cross-sectional dimension of 1300 μm × 150 μm and a material of copper was drawn in a lubricant (drawing speed: 10 m / min) for 1 hour to obtain a square wire with a length of 600 m. A 1 m long sample (a sample near the end of the 600 m wire) was extracted from the square wire after 1 hour of drawing, and linear scratches and curls were evaluated in the same manner as in Table 1. The results are shown in Table 7.

[0092] From Table 7, it was found that when either the angle variation |A - B| or the angle variation |C - D| is 3° or more, an evaluation of "C" is given in either linear scratches or curls.

[0093] When the average values of the reduction angles A and B are greater than the average values of the reduction angles C and B, it was found that an evaluation of "B" or higher can be obtained in the evaluation of linear scratches and curling.

[0094] It was found that if the sum of the angle variations |A - B| and |C - D| is less than 1°, an evaluation of "A" can be obtained in the evaluation of linear scratches and curling.

[0095] The length of the long sides 71, 72 / the length of the short sides 73, 74 is 11, and it was found that scratches or curling are likely to occur when there is a difference between the reduction angles A, B of the opposing surfaces and between the reduction angles C, D.

[0096] The embodiments disclosed this time should be considered as illustrative in all respects and not restrictive. The scope of the present invention is shown not by the above-described embodiments but by the claims, and it is intended that all meanings equivalent to the claims and all modifications within the scope are included.

Explanation of Reference Numerals

[0097] 1 Diamond, 2 Case, 3 Sintered alloy, 4 Support ring made of cemented carbide, 5 Polycrystalline diamond, 6 Inner surface of hole, 6a Bell, 6b Approach, 6c Reduction, 6d Bearing, 6e Back relief, 6f Exit, 7 Die hole, 7a, 7a1 Corner part, 7b1 Non-corner part, 71, 72 Long sides, 73, 74 Short sides, 100 Axis, 101, 102, 103, 104 Tangent lines, 200 Fixed part, 201 Wire, 201e Lower end.

Claims

1. A special-shaped die having a reduction from the upstream side in the wire drawing direction and a bearing having the smallest diameter adjacent to the reduction, a cross section of the bearing perpendicular to the wire drawing direction has a pair of long sides having a relatively long length and a pair of short sides having a relatively short length, In a cross section of the reduction parallel to the wiredrawing direction and intersecting the long side, an absolute value of a difference between a first reduction angle with respect to the wiredrawing direction and a second reduction angle opposite to the first reduction angle is 2° or less; In a cross section of the reduction parallel to the wiredrawing direction and intersecting the short side, an absolute value of a difference between a third reduction angle with respect to the wiredrawing direction and a fourth reduction angle opposite to the third reduction angle is 2° or less; An irregular shaped die, wherein an average value of the first reduction angle and the second reduction angle is greater than an average value of the third reduction angle and the fourth reduction angle.

2. The irregular die according to claim 1, wherein a ratio (D2 / D1) of the length D2 of the short side to the length D1 of the long side is 1 / 11 or more and 4 / 5 or less.

3. The irregular shaped die according to claim 1 or 2, wherein the first reduction angle and the second reduction angle are greater than or equal to 5° and less than or equal to 20°.

4. The irregular shaped die according to claim 1 or 2, wherein the length D2 of the short side is 10 μm or more and 10 mm or less.

5. The irregular die of claim 1 or 2, wherein the irregular die comprises polycrystalline diamond.

6. an absolute value of a difference between the first reduction angle and the second reduction angle is 0.5° or less; The irregular shaped die according to claim 1 or 2, wherein an absolute value of a difference between the third reduction angle and the fourth reduction angle is 0.5° or less.

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