Wire Drawing Dies

Abstract

The wiredrawing die has a bearing diameter D of less than 100 μm, a hole is provided in a polycrystalline diamond consisting essentially of diamond and having an average grain size of 500 nm or less, the reduction angle is 4° or more and 14° or less, the length of the bearing is 20% D or more and 100% D or less, the concentricity of the bearing and a bell or approach is 1.0 μm or less, and the circularity of the hole in the bearing is 0.5 μm or less.

Description

[Technical field]

[0001] The present disclosure relates to a wire drawing die. This application claims priority to Japanese Patent Application No. 2023-060736, filed on April 4, 2023. The entire contents of the Japanese Patent Application are incorporated herein by reference. [Background technology]

[0002] Conventionally, wire drawing dies are disclosed, for example, in WO 2008 / 088048. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2008 / 088048 Summary of the Invention

[0004] The wire drawing die of the present disclosure is a wire drawing die having a bearing diameter D of less than 100 μm, Holes are provided in a polycrystalline diamond consisting essentially of diamond and having an average grain size of 500 nm or less; The reduction angle is between 4° and 14°. The bearing length is between 20%D and 100%D. The concentricity of the bearing and the bell or approach is 1.0 μm or less. The roundness of the bearing bore is less than 0.5 μm. [Brief description of the drawings]

[0005] [Figure 1] FIG. 1 is a cross-sectional view of a binderless polycrystalline diamond die according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] [Problem that this disclosure aims to solve] Conventional wire drawing dies have the problem that it is difficult to produce thin wires.

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

[0008] The wiredrawing die of the present disclosure is a wiredrawing die having a bearing diameter D of less than 100 μm, a hole being provided in a polycrystalline diamond consisting essentially of diamond and having an average grain size of 500 nm or less, a reduction angle of 4° or more and 14° or less, a bearing length of 20% D or more and 100% D or less, a concentricity between the bearing and the bell or approach of 1.0 μm or less, and a circularity of the bearing hole of 0.5 μm or less.

[0009] (diamond) Polycrystalline diamond, which is essentially made of diamond, is a diamond that does not have a binder. A typical example 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. The average grain size in this application is calculated as follows. First, the sintered structure of polycrystalline diamond is observed with a SEM or TEM, and individual particles (primary particles) are extracted by image processing to calculate the area of ​​the particles, and the diameter of the area when it is assumed to be circular is taken as the grain size. Then, the average value of the grain size of each particle per unit area (for example, 50 μm × 50 μm) is taken as the average grain size.

[0010] The die hole generally has a circular shape in a cross section perpendicular to the wire drawing direction. (structure) The wire drawing die has, from the upstream side, a bell, an approach, a reduction, a bearing, a back relief, and an exit.

[0011] The reduction angle, which is the opening angle of the die hole in reduction, is 4° to 14°. If the reduction angle exceeds 14° or is less than 4°, the life of the wire drawing die will be shortened. The reduction angle is preferably 5° to 12°.

[0012] The length of the bearing is 20% D or more and 100% D or less, the concentricity of the bearing and the bell or approach is 1.0 μm or less, and the circularity of the bearing hole is 0.5 μm or less. Preferably, the length of the bearing is 30% D or more and 70% D or less. Preferably, the concentricity of the bearing and the bell or approach is 0.8 μm or less.

[0013] Fig. 1 is a cross-sectional view of a binderless polycrystalline diamond die according to an embodiment. As shown in Fig. 1, a wire drawing die 1 according to the embodiment has a die hole 1h. The die 1 has, in order from the upstream side, a bell 1a, an approach 1b, a reduction 1c, a bearing 1d, a back relief 1e, and an exit 1f.

[0014] Bell 1a is located at the most upstream side of die hole 1h. The angle α formed by tangents 12a, 13a to the side surface of die hole 1h that defines bell 1a is the bell angle. Bell 1a corresponds to the entrance for the wire to be drawn and the lubricant.

[0015] Approach 1b is provided downstream of bell 1a. At the boundary between bell 1a and approach 1b, the inclination of die hole 1h may change continuously or discontinuously. Angle β between tangents 12b and 13b of the side surface of die hole 1h that defines approach 1b is the approach angle.

[0016] The reduction 1c is provided downstream of the approach 1b. At the boundary between the approach 1b and the reduction 1c, the inclination of the die hole 1h may change continuously or discontinuously. The angle γ between the tangents 12c and 13c of the side surface of the die hole 1h that defines the reduction 1c is the reduction angle.

[0017] Bearing 1d is provided downstream of reduction 1c. At the boundary between reduction 1c and bearing 1d, the inclination of die hole 1h may change continuously or discontinuously. The diameter D of die hole 1h that defines bearing 1d is constant. Bearing 1d is cylindrical. Bearing 1d is the portion where the diameter is the smallest in die hole 1h.

[0018] Back relief 1e is provided downstream of bearing 1d. At the boundary between bearing 1d and back relief 1e, the inclination of die hole 1h may change continuously or discontinuously. The angle θ of the side surface of die hole 1h that defines back relief 1e is the back relief angle.

[0019] Exit 1f is provided downstream of back relief 1e. At the boundary between bearing 1d and back relief 1e, the inclination of die hole 1h may change continuously or discontinuously. The angle φ of the side surface of die hole 1h that defines back relief 1e is the exit angle.

[0020] If the diameter of reduction 1c is RD, then the relationship D < RD ≦ 1.050D holds between RD and D. Therefore, the portion having the diameter RD of the above relationship is reduction 1c. The cross-sectional area of reduction 1c is more than 100% and not more than 110% of the cross-sectional area of bearing 1d.

[0021] The length of bearing 1d is L. The relationship 20%D ≦ L ≦ 100%D holds between L and D. Preferably, the relationship 30%D ≦ L ≦ 70%D holds. The portion where the diameter of die hole 1h is D is bearing 1d.

[0022] (Method for specifying the shape of die hole 1h) In order to measure the shapes of the bell 1a, approach 1b, reduction 1c, bearing 1d, back relief 1e, and exit 1f, a transfer material (e.g., Repliset manufactured by Strauss Co., Ltd.) is filled into the die hole 1h to create a replica that transfers the shape of the die hole 1h. Using a tool microscope with transmitted illumination, this replica is used to clarify the contour of the die hole 1h and obtain a cross-sectional view of the die hole 1h like the die hole 1h in Fig. 1.

[0023] In the cross-sectional view, the part with the narrowest inner diameter and cylindrical shape is defined as the bearing 1d. Let the diameter of the bearing be D. In the cross-sectional view, the part located upstream of the bearing 1d and adjacent to the bearing 1d, where the inner diameter RD satisfies D < RD ≦ 1.050D, is defined as the reduction 1c. In the cross-sectional view, the part located downstream of the bearing 1d and adjacent to the bearing 1d, where the inner diameter BD satisfies D < BD ≦ 1.025D, is defined as the back relief 1e.

[0024] When measuring the reduction angle γ, in the cross-sectional view of the die hole 1h, tangents 12c and 13c are drawn on both sides at the reference point 11c (the part where RD = 1.050D) of the reduction 1c, and the angle formed by the two tangents 12c and 13c is defined as the reduction angle γ.

[0025] (Method for measuring concentricity) To measure the concentricity between the bell 1a or approach 1b and the bearing 1d, for example, a Keyence digital microscope (VH X8000) is used as the measuring device. The measurement conditions are a magnification of ×2,500 times and transmitted illumination. Observe the die hole 1h from a direction parallel to the center line 1p and obtain the contour of the region that appears white and shiny. For the diameter D of the die hole 1h, the outermost contour (bell or approach part) of the region that appears white and shiny within the range of 150 - 250%D is defined as the contour of the bell 1a or approach 1b. Approximate a circle from the contour and set the center of the circle as the center of the bell 1a or approach 1b. Similarly, obtain the contour of the bearing 1d. Approximate a circle from the contour and set the center of the circle as the center of the bearing 1d. The distance W between the center of the bell 1a or approach 1b and the center of the bearing 1d is defined as the concentricity.

[0026] (Method of measuring roundness) In this application, the roundness is defined as the difference between the maximum and minimum diameters when the diameter of the wire drawn through the die is measured in each direction of 360 degrees. A wire diameter measuring device (LDSN) manufactured by Celsa was used to measure the diameter of the drawn wire at 250 points over 360 degrees. The difference between the maximum and minimum values ​​of the 250 measured points is defined as the roundness. The shape of the die hole 1h (shape of the bearing 1d) is transferred to the wire, and the roundness of the bearing 1d is reflected in the wire.

[0027] The circularity of the bearing 1d is the difference between the maximum and minimum distances from the center of the bearing 1d obtained by circular approximation on the outline of the bearing 1d obtained by the above procedure.

[0028] [Details of the embodiment of the present disclosure] Example 1 (Wire drawing evaluation of BL (binderless) diamond dies) In order to confirm the effect of different die materials on performance, the following three types of dies with the same shape were prepared and evaluated.

[0029] Dice Material Three types of dies were prepared: A. Binderless PCD dies, B. Single crystal diamond dies, and C. PCD dies containing binder. The average grain size of the diamond in A. Binderless PCD dies is 0.05 μm (50 nm). The shapes of these dies are shown in Tables 1 and 2.

[0030] [Table 1]

[0031] [Table 2]

[0032] In Tables 1 and 2, "BLPCD" refers to a polycrystalline diamond produced by directly converting non-diamond carbon into diamond under ultra-high pressure and temperature, and which is essentially composed of diamond without the presence of a binder.

[0033] "PCD grain size 1 μm" refers to polycrystalline diamond that is composed of polycrystalline diamond with an average grain size of 1 μm, contains 5% or more by volume of binder, and the remainder is diamond.

[0034] Using this die, the SUS wire was drawn at a wire speed of 500 m / min under oil-based lubrication conditions. If the diameter D was φ0.08 mm, the wire diameter before drawing was φ0.087 mm. If the diameter D was φ0.10 mm, the wire diameter before drawing was φ0.109 mm. If the diameter D was φ0.04 mm, the wire diameter before drawing was φ0.0435 mm. If the diameter D was φ0.15 mm, the wire diameter before drawing was φ0.0164 mm. These SUS wires were drawn with each die, and the die life was determined to be the end of its life if the roundness of the wire after drawing was 0.3 μm or if the increase in wire diameter compared to the wire diameter of the drawn wire at 100 m after the start of drawing was 0.3 μm. Alternatively, the die life was determined to be the end of its life if curling (warping, R less than 30 mm) occurred in the wire. The results are shown in Tables 3 and 4.

[0035] [Table 3]

[0036] [Table 4]

[0037] In the "Lifespan" columns of Tables 3 and 4, "A" indicates a lifespan of 60 km or more, "B" indicates a lifespan of more than 30 km but less than 60 km, and "C" indicates a lifespan of 30 km or less.

[0038] "Wire diameter expansion" refers to the difference between the wire diameter 100m after the start of drawing and the wire diameter 30km after drawing. The wire diameter is the average value when the diameter of the wire drawn through the die is measured in each direction over 360 degrees. The measurement was performed using a wire diameter measuring device (LDSN) manufactured by Celsa, measuring the diameter of the drawn wire at 250 points over 360 degrees. There are also samples with a negative wire diameter expansion. This is because when a high-hardness diamond such as BLPCD is used, ring wear occurs, and the wire is scraped off and becomes thinner during drawing.

[0039] The "curl state" was rated as "A" if the curvature R of the wire after drawing was 50 mm or more, "B" if R was 30 mm or more but less than 50 mm, and "C" if R was less than 30 mm.

[0040] For dies with a lifespan of "C," the curl condition was poor from the beginning and worsened as the wiredrawing process progressed, making it impossible to draw 30 km of wire. Therefore, the roundness of the bearing at the end of its lifespan is recorded in "Circularity (after 30 km of wiredrawing)."

[0041] In sample number 166, wire breakage occurred at the stage of 5 km drawing. Since it was not possible to continue the evaluation, wire drawing was discontinued.

[0042] From Tables 3 and 4, it can be seen that a rating of B or higher was obtained in the evaluations of life, curl condition (initial), and curl condition (30 km) when the reduction angle was 14° or less, the bearing length was 20% D or more and 100% D or less, the concentricity between the bearing and the bell or approach was 1.0 μm or less, and the circularity of the bearing hole was 0.5 μm or less.

[0043] More preferably, it can be seen that when the reduction angle is between 5° and 12°, the evaluation of A increases. Furthermore, it can be seen that when the bearing length is between 30%D and 70%D, the evaluation of A increases. Furthermore, it can be seen that when the concentricity is 0.8μm or less, the evaluation of A increases.

[0044] (Appendix 1) A wire drawing die having a bearing diameter D of less than 100 μm, Holes are provided in a polycrystalline diamond consisting essentially of diamond and having an average grain size of 500 nm or less; The reduction angle is between 4° and 14°. The length of the bearing is greater than or equal to 20% D and less than or equal to 100% D, The concentricity of the bearing and the bell or approach is 1.0 μm or less, The wire drawing die, wherein the roundness of the bearing hole is 0.5 μm or less.

[0045] (Appendix 2) 2. The wire drawing die according to claim 1, wherein the reduction angle is greater than or equal to 5° and less than or equal to 12°.

[0046] (Appendix 3) 3. The wire drawing die according to claim 1 or 2, wherein the length of the bearing is 30% D or more and 70% D or less.

[0047] (Appendix 4) 4. The wire drawing die according to any one of claims 1 to 3, wherein the concentricity of the bearing and the bell or the approach is 0.8 μm or less.

[0048] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered as limiting. The scope of the present invention is defined by the claims, not by the embodiments described above, and is intended to include the equivalent meanings of the claims and all modifications within the scope of the claims. [Explanation of symbols]

[0049] 1 die, 1a bell, 1b approach, 1c reduction, 1d bearing, 1e back relief, 1f exit, 1h die hole, 1p center line, 11c reference point, 12a,12b,12c,13a,13b,13c tangents.

Claims

1. A wire drawing die having a bearing diameter D of less than 100 μm, Holes are provided in a polycrystalline diamond consisting essentially of diamond and having an average grain size of 500 nm or less; The reduction angle is between 4° and 14°. The length of the bearing is greater than or equal to 20% D and less than or equal to 100% D, The concentricity of the bearing and the bell or approach is 1.0 μm or less, The roundness of the hole of the bearing is less than or equal to 0.5 μm.

2. 2. The wire drawing die according to claim 1, wherein the reduction angle is greater than or equal to 5° and less than or equal to 12°.

3. 3. The wire drawing die according to claim 1, wherein the length of the bearing is 30% D or more and 70% D or less.

4. 3. The wire drawing die according to claim 1, wherein the concentricity between the bearing and the bell or the approach is 0.8 μm or less.

Images