Wire drawing processing method

Abstract

To uniformize a cross-sectional shape in the longitudinal direction of a wire material in a wire drawing processing method.SOLUTION: A first wire material having a first pipe material having a first longitudinal length and a second pipe material having a second longitudinal length different from the first longitudinal length is prepared, and a cross-sectional diameter of the first wire material is reduced by wire drawing processing to produce a second wire material having the first pipe material having a third longitudinal length and the second pipe material having a fourth longitudinal length different from the third longitudinal length. A first difference between the third longitudinal length and the fourth longitudinal length of the second wire material is made smaller than a second difference between the first longitudinal length and the second longitudinal length of the first wire material.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a wire drawing method and a wire drawing apparatus. [Background technology]

[0002] High-temperature superconducting wire is manufactured by filling a metal tube with the mixed powder, introducing a plurality of metal tubes filled with the mixed powder into a further tube, and processing the tube into a long and thin wire by a wire drawing method. This method is a wire drawing method generally used for metal tubes or metal rods. A drawing method, which is an example of a wire drawing method, is described in, for example, Patent Document 1.

[0003] The drawing method is a processing method in which the material is passed through a die hole having a hole diameter smaller than the maximum diameter of the material to be drawn, thereby reducing the cross-sectional diameter of the material in the same manner as the hole diameter. The process of passing the material through die holes with gradually decreasing die hole diameters is repeated multiple times until the desired cross-sectional diameter is reached. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2013-252565 A Summary of the Invention [Problem to be solved by the invention]

[0005] For example, a high-temperature superconducting wire is made up of a number of metal tubes, such as copper tubes, aluminum tubes, or iron tubes, each of which has a different deformation resistance, and the material made up of the number of metal tubes is subjected to wire drawing.

[0006] When using the drawing method, a long and thin wire is produced by repeatedly passing the material through a die hole. In the wire drawing process of a tube made of multiple tube materials, deformation starts from the metal tube located on the outermost side. Therefore, the metal tube located closer to the center in the cross-sectional direction tends to start to deform slower.

[0007] As a result, the material located on the outermost side is deformed first, resulting in a longer longitudinal length, whereas the material located in the center of the cross section is deformed later, resulting in a shorter longitudinal length.

[0008] For example, when a wire is made of metal materials with different deformation resistances, such as a high-temperature superconducting wire, the amount of deformation varies for each metal material, and therefore the longitudinal length also varies for each metal material. In order to obtain the shape characteristics required for a high-temperature superconducting wire, it is necessary to make the cross-sectional shape of the wire in the longitudinal direction uniform.

[0009] An object of the present invention is to make the cross-sectional shape of a wire rod in the longitudinal direction uniform in a wire drawing method. [Means for solving the problem]

[0010] A wiredrawing method according to one embodiment of the present invention is a wiredrawing method for reducing a cross-sectional diameter of a wire having at least a first tubular material and a second tubular material arranged around the first tubular material by wiredrawing, the method comprising the steps of: preparing a first wire having the first tubular material having a first longitudinal length and the second tubular material having a second longitudinal length different from the first longitudinal length; reducing the cross-sectional diameter of the first wire by the wiredrawing process to create a second wire having the first tubular material having a third longitudinal length and the second tubular material having a fourth longitudinal length different from the third longitudinal length; and making a first difference between the third longitudinal length and the fourth longitudinal length of the second wire smaller than a second difference between the first longitudinal length and the second longitudinal length of the first wire.

[0011] A wire drawing apparatus according to one aspect of the present invention includes a die having a hole diameter smaller than a maximum diameter of a wire having at least a first tube and a second tube provided around the first tube, and a gripping portion that grips one end of the wire and pulls it in a predetermined direction with a predetermined tensile force, the wire being passed through a hole of the die and pulled in the predetermined direction with the predetermined tensile force by the gripping portion gripping the end of the wire, thereby reducing a cross-sectional diameter of the wire. The wire drawing apparatus includes a first wire having a first longitudinal length and a second tube having a second longitudinal length different from the first longitudinal length. a first wire material is prepared, the first wire material is passed through the hole of the die, and the gripping portion gripping the end of the first wire material is pulled in the predetermined direction with the predetermined tensile force to reduce the cross-sectional diameter of the first wire material, thereby creating a second wire material having the first tubular material having a third longitudinal length and the second tubular material having a fourth longitudinal length different from the third longitudinal length, and a first difference between the third longitudinal length and the fourth longitudinal length of the second wire material is made smaller than a second difference between the first longitudinal length and the second longitudinal length of the first wire material. Effect of the Invention

[0012] According to one aspect of the present invention, in a wire drawing method, the cross-sectional shape of a wire in the longitudinal direction can be made uniform. [Brief description of the drawings]

[0013] [Figure 1] 1A and 1B are cross-sectional and side views of a material that is constructed into multiple metal tubes and bars. [Diagram 2] FIG. 1 is a simplified diagram of a drawing device. [Diagram 3] FIG. 1(a) is a side view of a material composed of a plurality of metal tubes and metal bars before drawing, and (b) and (c) are side views after drawing. [Figure 4] FIG. 1(a) is a side view of a material composed of a plurality of metal tubes and metal bars before drawing, and FIG. 1(b) is a side view of the material after drawing. [Diagram 5] FIG. 1( a ) is a side view of a material composed of a plurality of metal tubes and metal bars having the same deformation resistance before drawing, and FIG. 1( b ) is a side view of the material after drawing. [Figure 6] FIG. 1( a ) is a side view of a material composed of multiple metal tubes and metal bars with different deformation resistances, in which the metal tube located at the outermost periphery has low deformation resistance, before drawing, and FIG. 1( b ) is a side view of the material after drawing. [Figure 7] (a) is a simplified diagram of a drawing device, and (b) is a simplified diagram of a die. [Figure 8] FIG. 1( a ) is a side view of a material composed of multiple metal tubes and metal bars with different deformation resistances, in which the metal tubes located at the outermost periphery have the greatest deformation resistance, before drawing, and FIG. 1( b ) is a side view of the material after drawing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present invention will be described in detail below with reference to embodiments.

[0015] The embodiment relates to a wire drawing process for a high-temperature superconducting wire or a material composed of multiple metal tubes. For example, in the drawing process, the longitudinal length of the metal tubes differs depending on the metal tubes, so that both ends, which have different cross-sectional shapes, need to be cut.

[0016] As a result, when multiple drawing processes are performed, multiple cutting operations are also required. In order to obtain the performance of high-temperature superconducting wire, it is necessary to uniformize the cross-sectional shape in the longitudinal direction and reduce the number of steps in the wire drawing process.

[0017] For this reason, in the embodiment, for a material composed of multiple metal tubes or metal rods, the length of each metal tube or metal rod before processing is not made uniform, but is made to have shapes with different lengths and different wall thicknesses due to the deformation resistance and the arrangement of the material.

[0018] For example, the deformation resistance of the metal tube and the length before processing depending on the arrangement are examined using CAE (Computer Aided Engineering). In the CAE examination, the wire drawing process that reduces the maximum cross-sectional diameter of the material before wire drawing by 10% or more is examined using CAE.

[0019] The longitudinal length of each metal tube is measured when the cross-sectional diameter of the metal tube becomes 10% or more smaller than the initial cross-sectional diameter, and the difference between the longitudinal length of each metal tube material and the minimum longitudinal length of the metal tube is calculated, and the length of the metal tube before wire drawing is shortened by the difference.

[0020] According to the above embodiment, the number of cut portions at the end of the material is reduced by making the cross-sectional deformation in the length direction uniform in the wire drawing process. This reduces the loss of material. Furthermore, the reduction in the number of cutting steps makes it possible to reduce the number of steps in the wire drawing process, thereby reducing the manufacturing cost.

[0021] Hereinafter, the embodiments will be described with reference to the drawings. EXAMPLES

[0022] With reference to FIG. 1, an example of a wire material that is composed of a plurality of metal tubes and one metal rod will be described. 1, a metal tube 120 is disposed on the inner diameter side of a metal tube 110, and a metal rod 130 is disposed on the inner diameter side of the metal tube 120 to form a wire. The metal tube 110, the metal tube 120, and the metal rod 130 have the same length, different inner and outer diameters, and a cross-sectional shape of a circular arc. The length of the wire in the longitudinal direction is H1.

[0023] Methods for drawing a wire include drawing, cassette roll processing, groove roll processing, and the like. Of these methods, drawing will be taken as an example in the first embodiment.

[0024] The configuration of a drawing apparatus, which is an example of a wire drawing apparatus, will be described with reference to FIG. As shown in Fig. 2, the drawing device has a die 210 having a hole 230 and a gripping portion (chuck portion) 220. The wire 100 having an initial diameter D1 at end B5 is advanced by pulling the gripping portion 220 in the B4 direction with a predetermined tensile force while the end B6 of the wire 100 is gripped by the gripping portion 220. As a result, the cross-sectional diameter D1 at end B5 is reduced to the cross-sectional diameter D2 at end B6.

[0025] Specifically, the wire 100 is pulled in the B4 direction by the gripping portion 220, thereby passing the wire 100 through the hole 230 of the die 210. The wire 100 that has passed through the hole 230 of the die 210 has an initial diameter D1 that is smaller than the die diameter B7, and is reduced to a cross-sectional diameter D2. As a result, the cross-sectional diameter of the wire 100 that has passed through the hole 230 is reduced, while the length in the longitudinal direction is increased.

[0026] In the drawing process in which the cross-sectional diameter is reduced, deformation occurs from the outer diameter side of the wire 100, and as the cross-sectional reduction rate increases, that is, as the cross-sectional diameter becomes smaller, the deformation moves toward the cross-sectional center.

[0027] Furthermore, the metal tubes 110, 120 or metal rod 130, which have low deformation resistance, have a high deformation speed, and therefore the longitudinal length after drawing is longer than that of the metal tubes 110, 120 or metal rod 130, which have low deformation resistance before drawing. EXAMPLES

[0028] For a wire 100 composed of metal tubes 110, 120 and a metal rod 130 shown in FIG. 1, when the metal tubes 110, 120 and the metal rod 130 are made of materials having the same deformation resistance or materials having different deformation resistances, the length of each metal tube passing through the hole 230 of the die 210 of the drawing processing device shown in FIG. 2 will be different.

[0029] FIG. 3 shows the lengths H1 and H2 of the wire 100 in the longitudinal direction before and after the drawing process.

[0030] As shown in FIG. 3(a), the metal tubes 110, 120 and the metal rod 130 have the same length H1 and an initial diameter D1. After the cross-sectional diameter of the wire 100 shown in FIG. 3(a) is reduced from D1 to D2 by the drawing apparatus of FIG. 2, the wire 100 has a cross-sectional shape shown in FIG. 3(b) or FIG. 3(c).

[0031] 3(b), the longitudinal length of the metal rod 130 is the shortest length H2. The longitudinal length of the metal tube 110 is the longest length. The longitudinal length of the metal tube 110 is longer than H2 by H11. The longitudinal length of the metal tube 120 is longer than H2 by H12.

[0032] 3(c), the longitudinal length of the metal rod 130 is the shortest length H2. The longitudinal length of the metal tube 120 is the longest length. The longitudinal length of the metal tube 110 is longer than H2 by H12. The longitudinal length of the metal tube 120 is longer than H2 by H11.

[0033] As shown in FIG. 3(b), in a wire 100 in which the deformation resistances of the metal tubes 110, 120 and the metal rod 130 are the same, when the wire 100 having a longitudinal length H1 and a diameter D1 before the drawing process is subjected to the drawing process, the longitudinal length after the drawing process will be different.

[0034] 3(b), the length of the metal tube 110 located on the outermost side is longer than the length H2 of the metal rod 130 located at the center of the cross section after drawing by H11. The length of the metal tube 120 located on the inner diameter side of the metal tube 110 is longer than the length H2 of the metal rod 130 by H12.

[0035] 3(c), in the wire 100 in which the metal tubes 110, 120 and the metal rod 130 have different deformation resistances, the length of the metal tube 110 located on the outermost side is longer than the length H2 of the metal rod 130 located at the center of the cross section after drawing by H12. The length of the metal tube 120 located on the inner diameter side of the metal tube 110 is longer than the length H2 of the metal rod 130 by H11.

[0036] 5, in order to make the cross-sectional shape in the longitudinal direction of the wire 100 after drawing uniform, conditions for making the length of the wire 100 after drawing uniform using materials having the same deformation resistance will be considered. This consideration may be performed using, for example, CAE (Computer Aided Engineering).

[0037] 5(a), in the material 100 composed of the metal tube 110, the metal tube 120, and the metal rod 130, the length of the metal rod 130 is the longest at H1. The length of the metal tube 120 is H1-H11. The length of the metal tube 110 is H1-H12. After the cross-sectional diameter of the wire 100 shown in FIG. 5(a) is reduced from D1 to D2 by the drawing apparatus of FIG. 2, the wire 100 has a cross-sectional shape shown in FIG. 5(b).

[0038] 5(b), the length of the metal rod 130 in the longitudinal direction is the shortest length H2. The lengths of the metal tubes 110, 120 in the longitudinal direction are the longest lengths, which are longer than H2 by H16.

[0039] For example, the wire 100 having a length H1 and composed of a metal tube 110, a metal tube 120, and a metal rod 130 made of low carbon steel with the same deformation resistance was subjected to drawing to reduce the initial cross-sectional diameter D1 by 10 to 15% to a cross-sectional diameter D2, and lengths H11 and H12 (see FIG. 3(b)) were measured after the drawing process. As a result, it was confirmed that the length of the metal tube 110 was longer by H11, which corresponds to 20%, and the length of the metal tube 120 was longer by H12, which corresponds to 10%, of the shortest length H2 of the metal rod 130 after the drawing process.

[0040] The wire 100, which is composed of the metal tube 120 having a difference of H11 with respect to the length H1 of the metal rod 130, and the metal tube 110 having a difference of H12 with respect to the length H1 of the metal rod 130, was examined for the difference H16 of the wire 100 (see FIG. 5(b)) after the cross-sectional diameter was reduced from D1 to D2 by the drawing device of FIG. 2. As a result, it was confirmed that the difference H16 in length after drawing shown in FIG. 5(b) is sufficiently smaller than the differences H11 and H12 in length after drawing shown in FIG. 3(b). EXAMPLES

[0041] In the case of a wire 100 composed of metal tubes 110, 120 and a metal rod 130 shown in FIG. 1, when the metal tubes 110, 120 and the metal rod 130 have different deformation resistances and a material with low deformation resistance is used for the metal tube 110, the length of each metal tube passing through the hole 230 of the die 210 of the drawing processing device shown in FIG. 2 will be different.

[0042] FIG. 4 shows the lengths H1 and H2 of the wire 100 in the longitudinal direction before and after the drawing process.

[0043] 4(a) have different deformation resistances among the metal tube 110, the metal tube 120, and the metal rod 130. For example, in the case of the wire 100 in which the deformation resistances are greatest for the metal tube 130, the metal rod 110, and the metal tube 120 in that order, the metal tube 120 has the smallest deformation resistance and therefore undergoes deformation quickly. As shown in FIG. 4(a), the metal tubes 110, 120 and the metal rod 130 have the same length H1 and an initial diameter D1. After the cross-sectional diameter of the wire 100 shown in FIG. 4(a) is reduced from D1 to D2 by the drawing apparatus of FIG. 2, the wire 100 has a cross-sectional shape shown in FIG. 4(b).

[0044] 4(b), the length of the metal rod 130 in the longitudinal direction is the shortest length H2. The lengths of the metal tubes 110, 120 in the longitudinal direction are the longest lengths. The lengths of the metal tubes 110, 120 in the longitudinal direction are longer than H2 by H15.

[0045] As shown in Example 2, the metal tube 110 located at the outermost periphery deforms faster, and when processing is performed under the same conditions, the smaller the deformation resistance, the faster the deformation, so the deformation speed of the metal tube 120 with the smallest deformation resistance and the metal tube 110 located at the outermost periphery is faster. However, since the metal tube 110 located at the outermost periphery has a large deformation resistance, the deformation speed is suppressed and the lengths of the metal tube 110 and the metal tube 120 after drawing are approximately the same.

[0046] In this manner, in the wire 100 in which the deformation resistances of the metal tubes 110, 120 and the metal rod 130 are the same, when the wire 100 having a longitudinal length H1 and a diameter D1 before drawing is subjected to drawing, the longitudinal length after drawing will be different.

[0047] Specifically, compared to the length H2 of the metal rod 130 located at the center of the cross section after drawing, the length of the metal tube 110 located on the outermost side and the length of the metal tube 120 located on the inner diameter side of the metal tube 110 are longer than the length H2 of the metal rod 130 by H15.

[0048] 6, in order to make the cross-sectional shapes in the longitudinal direction of the wire 100 after drawing uniform, conditions for making the length of the wire 100 after drawing uniform using materials having different deformation resistances will be considered. This consideration may be performed using, for example, CAE.

[0049] 6(a), in the material 100 composed of the metal tube 110, the metal tube 120, and the metal rod 130, the length of the metal rod 130 is H1, which is the longest. The lengths of the metal tubes 110, 120 are H1-H15. After the cross-sectional diameter of the wire 100 shown in FIG. 6(a) is reduced from D1 to D2 by the drawing apparatus of FIG. 2, the wire 100 has a cross-sectional shape shown in FIG. 6(b).

[0050] 6(b), the length of the metal rod 130 in the longitudinal direction is the shortest length H2. The lengths of the metal tubes 110, 120 in the longitudinal direction are the longest lengths, which are longer than H2 by H19.

[0051] For example, as metal materials with different deformation resistances, metal tube 110 in Figure 6(a) is a low carbon steel tube, metal tube 120 is a pure aluminum tube, and metal bar 130 is a pure iron bar, and among the three metal materials, metal tube 110 has the highest deformation resistance and metal tube 120 has the lowest deformation resistance.

[0052] The wire 100 having a length H1 and composed of the metal tube 110, the metal tube 120, and the metal rod 130 was measured for its length H15 (see FIG. 4(b)) after drawing, in which the initial cross-sectional diameter D1 was reduced by 10 to 15% to a cross-sectional diameter D2. As a result, it was confirmed that the lengths of the metal tubes 110 and 120 were longer by H15, which corresponds to 16%, than the shortest length H2 of the metal rod 130 after drawing.

[0053] The wire 100, which is composed of the metal tubes 110, 120 and the metal rod 130 and has a difference of H15 from the length H1 of the metal rod 130, was examined for the difference H19 of the wire 100 (see FIG. 6(b)) after the cross-sectional diameter was reduced from D1 to D2 by the drawing device of FIG. 2. As a result, it was confirmed that the difference H19 in length after drawing shown in FIG. 6(b) is sufficiently smaller than the difference H15 in length after drawing shown in FIG. 4(b). EXAMPLES

[0054] The configuration of a drawing device for uniforming the length in the longitudinal direction in the first and second embodiments will be described with reference to FIG. The drawing apparatus shown in FIG. 7 differs from the drawing apparatus shown in FIG. 2 in that a new die 240 is additionally disposed.

[0055] In the drawing device, when the wire 100 has both ends B5 and B9, a gripping part 220 is provided at the end B9 and the wire 100 is pulled in the B4 direction. In addition, a die 240 is provided at the end B5 to limit deformation of the end B5 of the wire 100.

[0056] The die 240 is a die for restricting or adjusting the deformation in the longitudinal direction of the end B5 of the wire 100, and applies a pressing force in a direction B8 similar to the pulling direction B4 using a force different from the pulling force of the wire 100.

[0057] As shown in Fig. 7(b), the die 240 is provided with a groove 250 larger than the maximum diameter of the wire 100, and the end B5 of the wire 100 is placed in the groove 250. The pressing force in the direction B8 is set to 100% to 300% of the pulling force in the direction B4. Other configurations are the same as those of the drawing device shown in Fig. 2, so the description thereof will be omitted.

[0058] According to the above embodiment, the number of cut portions at the end of the material is reduced by making the cross-sectional deformation in the length direction uniform in the wire drawing process. This reduces the loss of material. Furthermore, the reduction in the number of cutting steps makes it possible to reduce the number of steps in the wire drawing process, thereby reducing the manufacturing cost. EXAMPLES

[0059] In the case of a wire 100 composed of metal tubes 110, 120 and a metal rod 130 shown in FIG. 1, when the metal tubes 110, 120 and the metal rod 130 have different deformation resistances and the metal tube 110 is made of a material with a high deformation resistance, the length of each metal tube passing through the hole 230 of the die 210 of the drawing processing device shown in FIG. 2 will be different.

[0060] 3(a) and 3(c) show the lengths H1 and H2 of the wire 100 in the longitudinal direction before and after the drawing process.

[0061] 3(a) have different deformation resistances among the metal tube 110, the metal tube 120, and the metal rod 130. For example, in the case of the wire 100 in which the deformation resistances are greatest for the metal tube 110, the metal rod 130, and the metal tube 120 in that order, the metal tube 110 has the greatest deformation resistance and therefore undergoes deformation slowly. As shown in FIG. 3(a), the metal tubes 110, 120 and the metal rod 130 have the same length H1 and an initial diameter D1. After the cross-sectional diameter of the wire 100 shown in FIG. 3(a) is reduced from D1 to D2 by the drawing apparatus of FIG. 2, the wire 100 has a cross-sectional shape shown in FIG. 3(c).

[0062] 3(c), the longitudinal length of the metal rod 130 is the shortest length H2. The longitudinal length of the metal tube 120 is the longest length. The longitudinal length of the metal tube 110 is longer than H2 by H12. The longitudinal length of the metal tube 120 is longer than H2 by H11.

[0063] As shown in Example 2, the metal tube 110 located at the outermost periphery deforms faster, and when processing is performed under the same conditions, the smaller the deformation resistance, the faster the deformation, so the deformation speed of the metal tube 120 with the smallest deformation resistance and the metal tube 110 located at the outermost periphery is faster. However, since the metal tube 110 located at the outermost periphery has a large deformation resistance, the deformation speed is suppressed and the length of the metal tube 110 after drawing is shorter than the length of the metal tube 120 after drawing.

[0064] In this manner, in the wire 100 having different deformation resistances of the metal tubes 110, 120 and the metal rod 130, when the wire 100 having a longitudinal length H1 and a diameter D1 before drawing is subjected to drawing, the longitudinal length after drawing will be different.

[0065] 3(c), the length of the metal tube 110 located on the outermost side is longer than the length H2 of the metal rod 130 located at the center of the cross section after drawing by H12. The length of the metal tube 120 located on the inner diameter side of the metal tube 110 is longer than the length H2 of the metal rod 130 by H11.

[0066] 8, in order to make the cross-sectional shapes in the longitudinal direction of the wire 100 after drawing uniform, conditions for making the length of the wire 100 after drawing uniform using materials having different deformation resistances will be considered. This consideration may be performed using, for example, CAE.

[0067] 8(a), in the material 100 composed of the metal tube 110, the metal tube 120, and the metal rod 130, the length of the metal rod 130 is the longest at H1. The length of the metal tube 110 is H1-H12. The length of the metal tube 120 is H1-H11.

[0068] The thickness of the metal tube 110 having a large deformation resistance is T1, and the thickness of the metal tube 120 having a small deformation resistance is T2. In this manner, the thickness T1 of the metal tube 110 is always made thicker than the thickness T2 of the metal tube 120.

[0069] After the cross-sectional diameter of the wire 100 shown in FIG. 8(a) is reduced from D1 to D2 by the drawing apparatus of FIG. 2, the wire 100 has a cross-sectional shape shown in FIG. 8(b).

[0070] 8(b), the length of the metal rod 130 in the longitudinal direction is the shortest length H2. The lengths of the metal tubes 110, 120 in the longitudinal direction are the longest lengths, which are longer than H2 by H19.

[0071] For example, as metal materials with different deformation resistances, the metal tube 110 in Figure 8(a) is a nickel alloy tube, the metal tube 120 is a pure aluminum tube, and the metal rod 130 is a pure aluminum rod, and of the three metal materials, the metal tube 110 has the greatest deformation resistance, and the metal tube 120 and the metal rod 130 have the smallest deformation resistances.

[0072] The wire 100 having a length H1 and composed of the metal tube 110, the metal tube 120, and the metal rod 130 was measured for its length after drawing (see FIG. 3(c)), in which the initial cross-sectional diameter D1 was reduced by 10 to 15% to a cross-sectional diameter D2 by drawing. As a result, it was confirmed that the length of the metal tube 110 was longer by H12, which corresponds to 10%, and the length of the metal tube 120 was longer by H11, which corresponds to 16%, of the shortest length H2 of the metal rod 130 after drawing.

[0073] The wire 100 (see FIG. 8(a)) consisting of the metal tube 110 with a thickness T1 having a difference of H12, the metal tube 120 with a thickness T2 having a difference of H11, and the metal rod 130 was examined for the difference H19 of the wire 100 (see FIG. 8(b)) after the cross-sectional diameter was reduced from D1 to D2 by the drawing device of FIG. 2. As a result, it was confirmed that the difference H19 in length after drawing shown in FIG. 8(b) is sufficiently smaller than the differences H11 and H12 in length after drawing shown in FIG. 3(c). [Explanation of symbols]

[0074] 100 wire rod 110 Metal tube 120 Metal tube 130 metal rod 210 Dice 220 Grip part 230 holes 240 Mold

Claims

1. A wire drawing method for reducing a cross-sectional diameter of a wire having at least a metal rod and a first metal tube provided on an outer periphery of the metal rod by wire drawing, comprising: A first wire is provided, the first wire including the metal rod having a first longitudinal length and the first metal tube having a second longitudinal length different from the first longitudinal length; a second wire is produced by reducing the cross-sectional diameter of the first wire through the wiredrawing process to produce the second wire, the second wire including the metal bar having a third longitudinal length and the first metal tube having a fourth longitudinal length different from the third longitudinal length; A wire drawing method, characterized in that a first difference between the third longitudinal length and the fourth longitudinal length of the second wire rod is made smaller than a second difference between the first longitudinal length and the second longitudinal length of the first wire rod.

2. preparing a third wire having the metal rod and the first metal tube, the lengths of which are equal to each other in a longitudinal direction; By the wire drawing process, the cross-sectional diameter of the third wire is reduced to produce a fourth wire having the metal bar having a fifth longitudinal length and the first metal tube having a sixth longitudinal length different from the fifth longitudinal length; The wiredrawing method according to claim 1, characterized in that a third difference between the fifth longitudinal length and the sixth longitudinal length of the fourth wire rod is set as the second difference of the first wire rod, and the second wire rod is created from the first wire rod by the wiredrawing.

3. the first longitudinal length of the metal rod in the first wire is longer than the second longitudinal length of the first metal tube by the second difference; The wire drawing method according to claim 1, characterized in that the third longitudinal length of the metal bar in the second wire is shorter than the fourth longitudinal length of the first metal tube by the first difference.

4. The wire drawing method according to claim 2, characterized in that the fifth longitudinal length of the metal bar in the fourth wire is shorter than the sixth longitudinal length of the first metal tube by the third difference.

5. 2. The wire drawing method according to claim 1, wherein the first difference is set to be smaller than the second difference so that the cross-sectional shape in the longitudinal direction of the second wire rod is made uniform at the end portion and the central portion. Processing method.

6. 2. The wire drawing method according to claim 1, wherein the wire is made of a superconducting wire having a cylindrical cross section.

7. the first wire rod has a second metal tube around the outer periphery of the first metal tube, the second metal tube having a length shorter than the second longitudinal direction; 2. The wire drawing method according to claim 1, wherein the first wall thickness of the first metal tube is thinner than the second wall thickness of the second metal tube.

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