Oxygen-free copper wire rod, method for manufacturing oxygen-free copper wire rod, and method for manufacturing oxygen-free copper casting.

Abstract

We provide oxygen-free copper wire with minimal surface scratches. [Solution] The oxygen-free copper wire has a diameter of 7.60 mm or more and a surface scratch height of 120 μm or less.

Description

Technical Field

[0008] , , ,

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[0001] The present disclosure relates to an oxygen-free copper drawn wire, a method for manufacturing an oxygen-free copper drawn wire, and a method for manufacturing an oxygen-free copper casting material.

Background Art

[0002] Patent Document 1 discloses a method for manufacturing a copper wire, comprising a step of preparing an upcast material produced by an upward casting method, and a step of producing a drawn wire by drawing the upcast material. The upcast material is formed of oxygen-free copper. The drawn wire is formed of oxygen-free copper.

Prior Art Documents

Patent Documents

[0003] [[ID=z1]]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] It is desired to manufacture an oxygen-free copper drawn wire with small surface scratches.

[0005] One object of the present disclosure is to provide an oxygen-free copper drawn wire with small surface scratches.

Means for Solving the Problems

[0006] The oxygen-free copper drawn wire of the present disclosure has a diameter of 7.60 mm or more and a height of surface scratches of 120 μm or less.

Effects of the Invention

[0007] The oxygen-free copper drawn wire of the present disclosure has small surface scratches.

Brief Description of the Drawings

[0008] [Figure 1]Figure 1 is a schematic perspective view showing an oxygen-free copper wire according to an embodiment. [Figure 2] Figure 2 is a first partial longitudinal cross-sectional view of the oxygen-free copper wire of the embodiment. [Figure 3] Figure 3 is a second partial longitudinal cross-sectional view of the oxygen-free copper wire of the embodiment. [Figure 4] Figure 4 is a first cross-sectional view showing a schematic of an upcasting apparatus used in the method for manufacturing oxygen-free copper castings according to the embodiment. [Figure 5] Figure 5 is a second cross-sectional view showing a schematic of the upcasting apparatus used in the method for manufacturing oxygen-free copper castings according to the embodiment. [Figure 6] Figure 6 is a third cross-sectional view showing a schematic of the upcasting apparatus used in the method for manufacturing oxygen-free copper castings according to the embodiment. [Figure 7] Figure 7 is a fourth cross-sectional view showing a schematic of the upcasting apparatus used in the method for manufacturing oxygen-free copper castings according to the embodiment. [Figure 8] Figure 8 is a cross-sectional view showing the procedure for adjusting the distance between the die and the cylindrical member in an upcasting apparatus used in the manufacturing method of oxygen-free copper castings according to the embodiment. [Modes for carrying out the invention]

[0009] [Description of Embodiments in this Disclosure] First, the embodiments of this disclosure will be listed and described.

[0010] (1) An oxygen-free copper wire according to one aspect of the present disclosure has a diameter of 7.60 mm or more and a surface scratch height of 120 μm or less.

[0011] When a coated copper wire is manufactured using the oxygen-free copper wire material described in (1) above, which has few surface scratches, blistering of the insulating coating is less likely to occur. This is thought to be because, due to the small surface scratches, air is less likely to accumulate between the oxygen-free copper wire material and the insulating coating when forming the coating. Blisters in the insulating coating can become electrical weak points. The oxygen-free copper wire material described in (1) above, which is less prone to blistering of the insulating coating, makes it easier to construct a coated copper wire with the desired voltage withstand characteristics.

[0012] (2) In the oxygen-free copper wire material described in (1) above, the height of the scratch may be 100 μm or less.

[0013] The oxygen-free copper wire material described in (2) above has even fewer defects, making it easier to construct coated copper wires with the desired voltage resistance characteristics.

[0014] (3) A method for manufacturing an oxygen-free copper wire according to one aspect of the present disclosure comprises the steps of: producing an oxygen-free copper casting having a diameter of 15.6 mm or more and 16.4 mm or less using an upcasting apparatus; and producing an oxygen-free copper wire having a diameter of 7.60 mm or more by drawing the oxygen-free copper casting. The upcasting apparatus comprises a die configured in the shape of a cylinder; a cylindrical member positioned above the die along the axis of the die; and a cooler positioned to surround the die and the cylindrical member. The distance between the die and the cylindrical member is 1.0 mm or more and 5.0 mm or less.

[0015] When the distance between the lower end of the cooler and the lower end of the cylindrical member is uniform, and the length of the die is uniform, an upcasting apparatus with a distance of 1.0 mm to 5.0 mm between the die and the cylindrical member is more likely to produce high-quality oxygen-free copper castings with fewer and smaller defects compared to an upcasting apparatus with a distance of less than 1.0 mm or more than 5.0 mm. The reason is as follows: When a die comes into contact with molten metal, it expands upward and downward due to thermal expansion. When the upper end of the die, which is expanding upward, comes into contact with the lower end of the cylindrical member, the die stops expanding upward. There is no member that restricts the downward expansion of the die. Therefore, when the upper end of the die, which is expanding upward, comes into contact with the lower end of the cylindrical member, the die expands downward by the amount it stopped expanding upward. When the spacing is 1.0 mm or more, compared to when the spacing is less than 1.0 mm, the wider spacing results in a longer length extending upwards and a shorter length extending downwards. As a result, when the spacing is 1.0 mm or more, the ratio of the contact area with the cooler to the outer surface area of ​​the die tends to be larger compared to when the spacing is less than 1.0 mm. Similarly, when the spacing is 5.0 mm or less, the ratio of the contact area with the cooler to the outer surface area of ​​the die tends to be larger compared to when the spacing is greater than 5.0 mm. Therefore, when the spacing is between 1.0 mm and 5.0 mm, the cooling performance of the die is higher compared to when the spacing is less than 1.0 mm or greater than 5.0 mm, making it easier for the molten metal to be cooled properly.

[0016] The method for manufacturing oxygen-free copper wire described in (3) above allows for the production of oxygen-free copper wire with fewer defects because it uses high-quality oxygen-free copper casting material for wire drawing. In other words, the method for manufacturing oxygen-free copper wire described in (3) above allows for the production of oxygen-free copper wire that is easy to construct into coated copper wire with desired voltage resistance characteristics.

[0017] (4) The method for manufacturing an oxygen-free copper casting material according to one aspect of the present disclosure includes a step of producing an oxygen-free copper casting material having a diameter of 15.6 mm or more and 16.4 mm or less by an up-cast casting apparatus. The up-cast casting apparatus includes a die configured in a cylindrical shape, a cylindrical member disposed above the die along the axis of the die, and a cooler disposed so as to surround the die and the cylindrical member. The distance between the die and the cylindrical member is 1.0 mm or more and 5.0 mm or less.

[0018] As described above, the method for manufacturing an oxygen-free copper casting material in (4) above can produce a high-quality oxygen-free copper casting material.

[0019] [Details of Embodiments of the Present Disclosure] Hereinafter, specific examples of the oxygen-free copper drawn wire and the method for manufacturing the oxygen-free copper drawn wire of the present disclosure will be described based on the drawings. The same reference numerals in the drawings denote the same objects. The shapes, sizes, positional relationships, etc. shown in each drawing are represented for the purpose of clarifying the explanation and do not necessarily represent the actual shapes, sizes, positional relationships, etc.

[0020] [Embodiment] [Oxygen-Free Copper Drawn Wire] Referring to FIGS. 1 to 3, the oxygen-free copper drawn wire 101 of the embodiment will be described. One of the characteristics of the oxygen-free copper drawn wire 101 of the embodiment is that, after the diameter D satisfies a specific range, the surface flaw 102 (FIGS. 2 and 3) is small.

[0021] [Composition] The oxygen-free copper drawn wire 101 shown in FIG. 1 is formed of pure copper containing 99.96% by mass or more of copper. The oxygen-free copper drawn wire 101 contains 99.99% by mass or more of copper and 0.0002% by mass or less of oxygen, and the balance may be inevitable impurities. The content ratios of copper and oxygen in the oxygen-free copper drawn wire 101 are ratios based on setting the total mass of the oxygen-free copper to 100% by mass. The composition can be determined, for example, by inductively coupled plasma optical emission spectrometry (ICP).

[0022] "shape" The oxygen-free copper wire rod 101 is, for example, a round wire. That is, the cross-sectional shape of the oxygen-free copper wire rod 101 is, for example, circular. The cross-section is a cross-section perpendicular to the axis of the oxygen-free copper wire rod 101.

[0023] "diameter" The diameter D of the oxygen-free copper wire 101 is 7.60 mm or more. The diameter D of the oxygen-free copper wire 101 is determined by cross-sectional observation using a scanning electron microscope (SEM). First, cross-sections are taken of 10 or more oxygen-free copper wires 101. The area of ​​the oxygen-free copper wire 101 in each cross-section is determined. The area of ​​the oxygen-free copper wire 101 with diameter D is determined using image analysis software. The average value of the equivalent diameter of an equal-area circle obtained by converting each area to a perfect circle is calculated. This average value is taken as the diameter D of the oxygen-free copper wire 101. Oxygen-free copper wire 101 with a diameter D of 7.60 mm or more is easy to use for various applications. The diameter D of the oxygen-free copper wire 101 may be, for example, 7.61 mm or more, or 7.62 mm or more. The diameter D of the oxygen-free copper wire 101 may be, for example, 8.38 mm or less. In other words, the diameter D of the oxygen-free copper wire 101 is 7.60 mm or more and 8.38 mm or less, 7.61 mm or more and 8.38 mm or less, or 7.62 mm or more and 8.38 mm or less.

[0024] "scratch" The height H of the surface defects 102 (Figures 2 and 3) on the oxygen-free copper wire 101 is 120 μm or less. Defects 102 are, for example, the crack 102a shown in Figure 2, or the protrusion 102b shown in Figure 3. Figures 2 and 3 show the longitudinal section of the oxygen-free copper wire 101. The longitudinal section is a section along the axis of the oxygen-free copper wire 101. Height H refers to the length of the protrusion from the surface or the recess from the surface of the defect 102. A 50 mm long sample is cut from any position on the oxygen-free copper wire 101, and the maximum value of the protrusion from the surface or the recess from the surface of the defect 102 on the surface of the sample is considered to be the height H of the defect 102 on the surface of the oxygen-free copper wire 101.

[0025] The flaw 102 can be detected using at least one of an image recognition device, an eddy current flaw detector, an ultrasonic flaw detector, and a laser flaw inspection device. The image recognition device detects the flaw 102 using an image captured by an imaging device. For example, the flaw 102 can be detected by automatic confirmation through image processing such as binarization. The eddy current flaw detector detects the flaw 102 using changes in current. For example, when a detection coil carrying alternating current is brought close to a sample, a certain amount of eddy current flows through the sample. If a flaw 102 is present, the eddy current will bypass the flaw 102, causing a change in the current value of the detection coil. The presence or absence of the flaw 102 can be detected by this change. The ultrasonic flaw detector detects the flaw 102 using the reflection of ultrasound. For example, ultrasound transmitted from an ultrasonic sensor is reflected off the surface of the sample and received by the ultrasonic sensor, where it is converted into a voltage. A difference in the converted voltage occurs depending on the presence or absence of the flaw 102, and the presence or absence of the flaw 102 can be detected from this voltage difference. The laser flaw inspection device detects the flaw 102 using the reflection of laser light. For example, when a laser beam is shone onto the surface of a sample, the position where the laser light is reflected changes depending on whether or not there is a scratch 102. The scratch 102 can be detected from this difference in the position where the laser light is reflected.

[0026] The height H of each detected scratch 102 can be determined by cross-sectional observation of each scratch 102. A longitudinal section of the sample is taken. Images are captured of the longitudinal section including the location where each scratch 102 is formed. In each image, the length of each scratch 102 along the direction perpendicular to the sample axis is determined. The direction perpendicular to the sample axis is the direction along the top and bottom in Figures 2 and 3. Of the multiple scratches 102, the maximum length of each scratch 102 along the direction perpendicular to the sample axis is taken as the height H of the scratch 102 on the surface of the oxygen-free copper wire 101.

[0027] If the height H of the surface scratches 102 is 120 μm or less, when a coated copper wire is manufactured with an insulating coating on the surface of the oxygen-free copper wire 101, blistering of the insulating coating is less likely to occur. The smaller the height H of the surface scratches 102, the less likely blistering of the insulating coating is to occur. The height H of the surface scratches 102 may be 100 μm or less, 95 μm or less, or 90 μm or less. For example, the height H of the surface scratches 102 is 30 μm or more. That is, the height H of the surface scratches 102 is 30 μm or more and 120 μm or less, 30 μm or more and 100 μm or less, 30 μm or more and 95 μm or less, or 30 μm or more and 90 μm or less.

[0028] <Manufacturing method for oxygen-free copper wire> The method for manufacturing oxygen-free copper wire according to the embodiment will be described with reference to Figures 4 to 7. The method for manufacturing oxygen-free copper wire according to the embodiment comprises a step A in which an oxygen-free copper casting material 100 (Figure 7) is produced using an upcasting apparatus 1, and a step B in which an oxygen-free copper wire 101 (Figure 1) is produced by drawing the oxygen-free copper casting material 100. One of the features of the method for manufacturing oxygen-free copper wire according to the embodiment is that in step A an oxygen-free copper casting material 100 having a specific diameter is produced using a specific upcasting apparatus 1, and in step B an oxygen-free copper wire 101 having a specific diameter D is produced.

[0029] Upcasting equipment The upcasting apparatus 1 produces oxygen-free copper casting material 100 (Figure 7) by drawing molten metal 10 upwards, passing it through a die 2, and allowing it to solidify. The upcasting apparatus 1 comprises a die 2, a cap 25, a cylindrical member 3, a cooler 4, a start bar 5, a rod-shaped member 6, a refractory member 7, a tundish 81, and a pinch roll 9.

[0030] [Dice] Die 2 solidifies the molten metal 10. The material of die 2 is, for example, graphite. The shape of die 2 is cylindrical. That is, the shape of the oxygen-free copper casting material 100 produced is cylindrical. The inner diameter of die 2 is uniform along the axis of die 2. That is, the outer diameter of the oxygen-free copper casting material 100 produced is uniform along the axis of oxygen-free copper casting material 100. The inner diameter of die 2 is between 16.25 mm and 16.35 mm. Because the inner diameter of die 2 is between 16.25 mm and 16.35 mm, an oxygen-free copper casting material 100 (Figure 7) having a diameter between 15.6 mm and 16.4 mm is produced. The outer diameter of die 2 gradually decreases from the lower end of die 2 located at the bottom of Figure 4 to the upper end of die 2 located at the top of Figure 4. That is, the outer surface of die 2 tapers from the lower end to the upper end. The die 2 has, in order from the lower end to the upper end, a first portion 21 that protrudes downward from the cooler 4 and the refractory member 7, and a second portion 22 that is fitted into the inner circumferential surface of the cooler 4. The lower end of the die 2 is placed in the molten metal 10. Before casting begins, a cap 25 is fitted to the opening at the lower end of the die 2.

[0031] [Cylindrical member] The cylindrical member 3 cools the oxygen-free copper casting material 100 that has passed through the die 2. The material of the cylindrical member 3 is, for example, graphite. The shape of the cylindrical member 3 is cylindrical. The inner and outer diameters of the cylindrical member 3 are uniform along the axis of the cylindrical member 3. The inner diameter of the cylindrical member 3 is the same as the inner diameter of the die 2. The cylindrical member 3 is positioned above the die 2 along the axis of the die 2 inside the cooler 4. The cylindrical member 3 is fixed inside the cooler 4.

[0032] A gap C is provided between the die 2 and the cylindrical member 3. The gap C is between 1.0 mm and 5.0 mm. When the distance between the lower end of the cooler 4 and the lower end of the cylindrical member 3 is uniform and the length of the die 2 is uniform, the upcasting apparatus 1 with a gap C of 1.0 mm to 5.0 mm is more likely to produce high-quality oxygen-free copper casting material 100 with fewer and smaller defects compared to upcasting apparatuses with a gap C of less than 1.0 mm or greater than 5.0 mm. The reason is as follows: The die 2, in contact with the molten metal 10, expands upward and downward due to thermal expansion. When the upper end of the die 2, which is expanding upward, comes into contact with the lower end of the cylindrical member 3, the die 2 stops expanding upward. There is no member that restricts the downward expansion of the die 2. Therefore, when the upper end of the die 2, which extends upward, comes into contact with the lower end of the cylindrical member 3, the die 2 extends downward by the amount by which it can no longer extend upward. When the spacing C is 1.0 mm or more, the spacing C is wider compared to when the spacing C is less than 1.0 mm, so the length of the die 2 extending upward becomes longer and the length of the die 2 extending downward becomes shorter. As a result, when the spacing C is 1.0 mm or more, the ratio of the contact area with the cooler 4 to the outer surface area of ​​the die 2 tends to be larger compared to when the spacing C is less than 1.0 mm. Similarly, when the spacing C is 5.0 mm or less, the ratio of the contact area with the cooler 4 to the outer surface area of ​​the die 2 tends to be larger compared to when the spacing C is greater than 5.0 mm. Therefore, when the spacing C is 1.0 mm or more and 5.0 mm or less, the cooling performance of the die 2 is higher compared to when the spacing C is less than 1.0 mm or greater than 5.0 mm, so the molten metal 10 is more easily cooled appropriately. The spacing C may be 1.5 mm or more and 4.5 mm or less, or 2.0 mm or more and 4.0 mm or less.

[0033] 〔cooler〕 The cooler 4 cools the die 2 and the cylindrical member 3. The cooler 4 surrounds the outer circumferential surfaces of the second portion 22 of the die 2 and the cylindrical member 3 so as to be in contact with them. The shape of the cooler 4 is cylindrical. The cooler 4 has, in order from the bottom end to the top end, a first portion 41 into which the second portion 22 of the die 2 is fitted, and a second portion 42 to which the cylindrical member 3 is fixed. The inner diameter of the first portion 41 of the cooler 4 gradually narrows upward. The inner diameter of the second portion 42 of the cooler 4 is uniform along the axis of the cooler 4. The material of the cooler 4 is a metal such as copper or a copper alloy. The cooler 4 has a flow path 45 through which cooling water 46 flows between the inner and outer circumferential surfaces. The flow path 45 is provided in the region of the cooler 4 except near the top and bottom ends. The cooler 4 itself is cooled by the cooling water 46 flowing through the channel 45, and the die 2 and cylindrical member 3 in contact with the inner circumferential surface of the cooler 4 are cooled.

[0034] [Start bar] As shown in Figure 4, the start bar 5 is inserted inside the die 2 or the cylindrical member 3 before casting begins, and is pushed down by the rod-shaped member 6 at the start of casting, pushing the cap 25 into the molten metal 10, as shown in Figure 5. The start bar 5 and the rod-shaped member 6 are separate and independent components. After dropping the cap 25 into the molten metal 10, the start bar 5 is pushed upward to the position of the pinch roll 9 as the molten metal 10 rises, as shown in Figure 6, and is further pulled upward by the pinch roll 9. The start bar 5 is discharged upward from the cylindrical member 3, as shown in Figure 7. The lower end of the start bar 5 is connected to the oxygen-free copper casting material 100, which has come into contact with the molten metal 10 and solidified. That is, the start bar 5 and the oxygen-free copper casting material 100 are discharged upward together. The shape of the start bar 5 is cylindrical. The outer diameter of the start bar 5 is smaller than the inner diameter of the die 2.

[0035] The start bar 5 is made of copper. When the start bar 5 comes into contact with the molten metal 10, there is a risk that components of the start bar 5 may be mixed into the molten metal 10. Alternatively, when the start bar 5 drops the cap 25, there is a risk that the rod-shaped member 6 may push the start bar 5 too hard, causing the start bar 5 itself to fall into the molten metal 10. In this case, components of the start bar 5 will be mixed into the molten metal 10. Conventional start bars 5 are made of iron-based materials. By making the start bar 5 out of copper, it is possible to manufacture an oxygen-free copper casting material 100 with a lower impurity content, even if components of the start bar 5 are mixed into the molten metal 10, compared to when the start bar 5 is made out of iron-based materials. In other words, by making the start bar 5 out of copper, it is possible to manufacture an oxygen-free copper casting material 100 with high conductivity.

[0036] The copper forming the start bar 5 may be oxygen-free copper. Oxygen-free copper is pure copper containing 99.96% by mass or more of copper. If the start bar 5 is formed from oxygen-free copper containing 99.96% by mass or more of copper, an oxygen-free copper casting material 100 with an even lower impurity content can be manufactured. That is, if the start bar 5 is formed from oxygen-free copper containing 99.96% by mass or more of copper, an oxygen-free copper casting material 100 with an even higher conductivity can be manufactured. The oxygen-free copper forming the start bar 5 may contain 99.99% by mass or more of copper and 0.0002% by mass or less of oxygen, with the remainder being unavoidable impurities. If the start bar 5 is formed from oxygen-free copper containing 99.99% by mass or more of copper, an oxygen-free copper casting material 100 with an even lower impurity content can be manufactured. In other words, if the start bar 5 is made of oxygen-free copper containing 99.99% by mass or more of copper, an oxygen-free copper casting material 100 with even higher conductivity can be manufactured. The proportion of copper and oxygen in oxygen-free copper is a ratio based on the total mass of oxygen-free copper being 100% by mass.

[0037] [Tandish] The tundish 81 is a container for temporarily storing molten metal 10 supplied from a melting furnace (not shown). The tundish 81 is covered with a cover 82 or the like to prevent the molten metal 10 inside from being exposed to the atmosphere. The cover 82 is provided with a through hole into which a refractory member 7 is fitted. A refractory seal (not shown) is provided between the inner circumferential surface of the through hole in the cover 82 and the outer circumferential surface of the refractory member 7 to prevent the molten metal 10 from passing through.

[0038] <Molten metal> The molten metal 10 is formed from oxygen-free copper. The oxygen-free copper forming the molten metal 10 is pure copper containing 99.96% by mass or more of copper. The oxygen-free copper forming the molten metal 10 contains 99.99% by mass or more of copper and 0.0002% by mass or less of oxygen, with the remainder being unavoidable impurities. The ratio of copper and oxygen content in the oxygen-free copper is calculated by taking the total mass of the oxygen-free copper as 100% by mass.

[0039] [Pinch roll] A pair of pinch rolls 9 transport the oxygen-free copper casting material 100 by gripping it. In the initial stages of lifting, the pair of pinch rolls 9 sequentially transport the rod-shaped member 6 and the start bar 5 by gripping them. The pair of pinch rolls 9 are positioned above the cooler 4.

[0040] [Fire-resistant material 7] The refractory member 7 protects the cooler 4 from the molten metal 10. The refractory member 7 can prevent the temperature of the cooler 4 from rising due to the heat of the molten metal 10, and can prevent the temperature of the molten metal 10 from decreasing due to the cooling from the cooler 4. The material of the refractory member 7 is, for example, graphite. The refractory member 7 covers the outer circumference of the lower part of the cooler 4 from the lower end. The refractory member 7 has a bottom and a side wall. A through hole is provided in the center of the bottom. The second part 22 of the die 2 is inserted through this through hole. A refractory seal (not shown) is provided between the inner surface of the through hole and the outer surface of the second part 22 of the die 2 to prevent the molten metal 10 from passing through. The side wall is positioned between the inner surface of the through hole in the cover 82 and the outer surface of the cooler 4. The side wall is connected to the periphery of the bottom. The side wall protrudes upward from the periphery of the bottom.

[0041] ≪Process A≫ Step A involves producing an oxygen-free copper casting material 100 using the upcasting apparatus 1 shown in Figure 4. Step A includes step a1 of preparing the upcasting apparatus 1 and step a2 of removing the cap 25 using the start bar 5.

[0042] [Step a1] In step a1, the upcasting apparatus 1 is prepared in the following procedure: A first assembly is prepared in which a cylindrical member 3 is fixed inside the cooler 4. A second assembly is produced in which the die 2 is press-fitted into the first part 41 of the cooler 4 by pushing the die 2 into the first part 41 of the cooler 4 from the opening at the lower end of the cooler 4 in the first assembly. The die 2 is pushed in such a way that the gap C between the die 2 and the cylindrical member 3 is between 1.0 mm and 5.0 mm. The die 2 is pushed in, for example, by striking the lower end of the die 2 inserted into the first part 41 of the cooler 4 with a hammer. As described above, the outer surface of the die 2 tapers from the lower end to the upper end, and as described above, the inner surface of the first part 41 of the cooler 4 tapers from the bottom to the top. Therefore, by pushing the die 2 into the first part 41 of the cooler 4, the die 2 can be press-fitted into the first part 41 of the cooler 4.

[0043] After press-fitting, measure whether the gap C is between 1.0 mm and 5.0 mm. In this example, the jig 200 shown in Figure 8 is used to measure the gap C. Figure 8 shows the second set of parts arranged horizontally. The jig 200 has a rod-shaped part 201 and a tip part 202. The shape of the rod-shaped part 201 is cylindrical. The outer diameter of the rod-shaped part 201 is smaller than the inner diameter of the die 2. A scale (not shown) is provided on the outer surface of the rod-shaped part 201. The tip part 202 is provided at the tip of the rod-shaped part 201. The shape of the tip part 202 is disc-shaped. The outer diameter of the tip part 202 is larger than the outer diameter of the rod-shaped part 201 and smaller than the inner diameter of the die 2. The thickness of the tip part 202 is, for example, between 0.5 mm and 1.0 mm. The thickness of the tip part 202 is the length along the axis of the rod-shaped part 201. The tip portion 202 is less likely to be damaged when it comes into contact with the lower end of the cylindrical member 3, as will be described later, because the thickness of the tip portion 202 is 0.5 mm or more. The tip portion 202 is less than or equal to 1.0 mm, so that it can be positioned between the die 2 and the cylindrical member 3 when the gap C is 1.0 mm or more, making it easier to measure that the gap C is between 1.0 mm and 5.0 mm. The gap C is measured using the jig 200 as follows.

[0044] As shown in the upper part of Figure 8, the tip portion 202 is inserted into the inside of the die 2. As shown in the center part of Figure 8, the rod-shaped portion 201 is moved toward the cylindrical member 3, thereby moving the tip portion 202 toward the cylindrical member 3 and dropping it between the die 2 and the cylindrical member 3. The rod-shaped portion 201 is moved toward the end face of the die 2, by bringing the tip portion 202 into contact with the end face of the die 2. The end face of the die 2 is the face facing the cylindrical member 3, which is the left end face in Figure 5. As shown in the lower part of Figure 8, the rod-shaped portion 201 is moved toward the end face of the cylindrical member 3, by bringing the tip portion 202 into contact with the end face of the cylindrical member 3. The end face of the cylindrical member 3 is the face facing the end face of the die 2, which is the right end face in Figure 5. The distance from the point where the tip 202 contacts the end face of the die 2 to the point where it contacts the end face of the cylindrical member 3 is calculated as the sum of the distance and the thickness of the tip 202. This sum is the interval C. The distance from the point where the tip 202 contacts the end face of the die 2 to the point where it contacts the end face of the cylindrical member 3 is determined by the difference between the first scale and the second scale. The first scale is the scale of the rod-shaped portion 201 that overlaps with the lower end of the die 2 when the tip 202 contacts the end face of the die 2. The second scale is the scale of the rod-shaped portion 201 that overlaps with the lower end of the die 2 when the tip 202 contacts the end face of the cylindrical member 3.

[0045] Unlike this example, a microscope may be used to measure the interval C. Insert the microscope into the die 2. Capture an image using the microscope that includes the upper end of the die 2 and the lower end of the cylindrical member 3 within the same field of view. The interval C can be determined by analyzing the captured image.

[0046] Unlike this example, the spacing C may also be determined by distance L1 - (total length L2 - length L3). Distance L1 is the distance between the end face of the cylindrical member 3 and the lower end of the cooler 4 before the die 2 is pressed into the cooler 4. Total length L2 is the total length of the die 2. Length L3 is the length of the die 2 that is exposed from the end face of the cooler 4 after the die 2 has been pressed in.

[0047] If the spacing C is between 1.0 mm and 5.0 mm, the cap 25 is attached to the opening at the lower end of the die 2. The first part 21 of the die 2 is inserted into the through hole at the bottom of the fire-resistant material 7 attached to the cover 82 of the tundish 81.

[0048] If the gap C is greater than 5.0 mm, die 2 may be pushed in further. Then, the gap C is measured. The process of pushing die 2 in further and measuring the gap C is repeated until the gap C is between 1.0 mm and 5.0 mm. Alternatively, if the gap C is greater than 5.0 mm, die 2 may be pulled out from inside the first part 41 of the cooler 4, and the pulled-out die 2 or a new die 2 may be pushed into the first part 41 of the cooler 4. Then, the gap C is measured. The process of pushing die 2 in further and measuring the gap C is repeated until the gap C is between 1.0 mm and 5.0 mm.

[0049] If the gap C is less than 1.0 mm, the die 2 is withdrawn from inside the first part 41 of the cooler 4, and the withdrawn die 2 or a new die 2 is pushed into the first part 41 of the cooler 4. Then, the gap C is measured. The process of pushing in the die 2 and measuring the gap C is repeated until the gap C is between 1.0 mm and 5.0 mm.

[0050] Unlike this example, resin may be used to measure the gap C. Specifically, resin is poured between the upper end of die 2 and the lower end of cylindrical member 3 and allowed to solidify. Die 2 is withdrawn, and the solidified resin is also withdrawn. The thickness of the solidified resin at the portion corresponding to the space between the upper end of die 2 and the lower end of cylindrical member 3 is measured. Then, the withdrawn die 2 or a new die 2 is pushed in so that the gap C is between 1.0 mm and 5.0 mm.

[0051] [Step a2] In step a2, the rod-shaped member 6 is lowered. The rod-shaped member 6 may also be lowered by rotating a pair of pinch rolls 9. The lowered rod-shaped member 6 pushes the start bar 5 downward, causing the start bar 5 to push the cap 25 and drop it into the molten metal 10. Once the cap 25 falls into the molten metal 10, the molten metal 10 is pulled up into the die 2 by the liquid pressure corresponding to the distance from the liquid surface of the molten metal 10. The molten metal 10 is cooled and solidified as it passes through the die 2 and the cylindrical member 3 in sequence. This solidification produces an oxygen-free copper casting material 100 having a diameter D of 15.6 mm or more and 16.4 mm or less. The produced oxygen-free copper casting material 100 is pulled up by a pair of pinch rolls 9. The pulled-up oxygen-free copper casting material 100 is wound onto a roll (not shown).

[0052] ≪Process B≫ Process B involves drawing an oxygen-free copper wire rod 101 from an oxygen-free copper casting 100. The number of passes in the wire drawing process, the degree of processing per pass, and the total degree of processing can be appropriately selected to obtain an oxygen-free copper wire rod 101 having a diameter of 7.60 mm or more and 8.38 mm or less, and are not particularly limited. Known values ​​for the number of passes, degree of processing per pass, and total degree of processing can be adopted. The wire drawing process in each pass is, for example, cold drawing.

[0053] In process A, as described above, by having a spacing C of 1.0 mm or more and 5.0 mm or less, a high-quality oxygen-free copper casting material 100 with few and small defects can be produced. In process B, the high-quality oxygen-free copper casting material 100 is drawn, so an oxygen-free copper wire rod 101 with few defects 102 can be produced.

[0054] [Example Test] In the test example, the difference in surface defect height H in the drawn wire was investigated due to the difference in the spacing C described above.

[0055] <Sample No. 1 to Sample No. 3> The drawn wires of samples No. 1 to No. 3 were manufactured using the oxygen-free copper wire manufacturing method described above. Specifically, the drawn wires of samples No. 1 to No. 3 were manufactured by performing step A, in which an oxygen-free copper casting is produced using the upcasting apparatus 1 shown in Figure 4, and step B, in which oxygen-free copper wires are produced by drawing the oxygen-free copper casting.

[0056] ≪Process A≫ In the upcasting apparatus 1, the inner diameter of the die 2 and the inner diameter of the cylindrical member 3 were set to 16 mm, and the distance C between the die 2 and the cylindrical member 3 was set to the value shown in Table 1. The molten metal was made of oxygen-free copper. In process A, an oxygen-free copper casting material with a diameter of 16 mm was produced using the upcasting apparatus 1.

[0057] ≪Process B≫ Oxygen-free copper wire with a diameter of 8 mm and a length of 1000 m was produced by drawing oxygen-free copper casting. The drawing process consisted of 7 passes, with a processing degree of 10.7% per pass. The total processing degree was 75%. The total processing degree is calculated by dividing the difference between the cross-sectional area of ​​the oxygen-free copper casting and the cross-sectional area of ​​the oxygen-free copper wire after final drawing by the cross-sectional area of ​​the oxygen-free copper casting.

[0058] <Sample No. 101 to Sample No. 103> The drawn wires of samples No. 101 to No. 103 were manufactured in the same manner as sample No. 1, etc., except that the distance C between the die 2 and the cylindrical member 3 was different, as shown in Table 1.

[0059] <Measuring the length of the wound> A 200mm length sample was cut from an arbitrary position in a 1000m length of oxygen-free copper wire, and the maximum protrusion or recess length from the surface of a defect on the sample surface was determined. The defect was detected using an eddy current flaw detector. The eddy current flaw detector used was a DEFECTOMAT® DA manufactured by Nippon Förster Co., Ltd. The length of the defect was determined from the observation image of the longitudinal section of the sample.

[0060] <Measurement of the frequency of swelling> Insulated copper wires were fabricated by forming an insulating coating on the outer surface of oxygen-free copper wire rods of each sample, and the frequency of blistering of the insulating coating was investigated. The insulating coating was formed from polyimide. The thickness of the insulating coating was set to 13 μm. The frequency of blistering was determined by counting the number of blister locations on the in-running insulated copper wire using a commercially available flaw detection device. The results are shown in Table 1. In Table 1, the frequency of blistering is shown as the number of blister locations per 100 kg of insulated copper wire (locations / 100 kg).

[0061] [Table 1]

[0062] As shown in Table 1, the height of surface scratches in oxygen-free copper wire samples No. 1 to No. 3 was smaller than the height of surface scratches in oxygen-free copper wire samples No. 101 to No. 103. The height of the scratches in samples No. 1 to No. 3 was 120 μm or less, and furthermore, 50 μm or less. The frequency of blistering in coated copper wires of samples No. 1 to No. 3 was less than the frequency of blistering in coated copper wires of samples No. 101 to No. 103. The frequency of blistering in samples No. 1 to No. 3 was 0.10 locations / 100 kg or less, and furthermore, 0.05 locations / 100 kg or less.

[0063] The present invention is not limited to the configurations shown in the embodiments, but is intended to include all modifications within the meaning and scope of the claims as indicated by the claims. [Explanation of Symbols]

[0064] 1 Upcasting apparatus 2 dice 21 Part 1 22 Part 2 25 caps 3. Cylindrical member 4. Cooler 41 Part 1 42 Part 2 45 flow channels 46 Cooling water 5 Start bar 6. Rod-shaped member 7 Fire-resistant materials 81 Tan Dish 82 Cover 9 Pinch roll 10 Molten metal 100 Oxygen-free copper casting material 101 Oxygen-free copper wire 102 wounds 102a Crack 102b Protrusion 200 jigs 201 Rod-shaped part 202 Tip C interval D diameter H Height

Claims

1. The diameter is 7.60 mm or more. The height of the surface scratches is 120 μm or less. Oxygen-free copper wire.

2. The oxygen-free copper wire material according to claim 1, wherein the height of the aforementioned defect is 100 μm or less.

3. A process for producing oxygen-free copper castings having a diameter of 15.6 mm or more and 16.4 mm or less using an upcasting apparatus, The process includes a step of producing an oxygen-free copper wire having a diameter of 7.60 mm or more by drawing the oxygen-free copper casting material, The upcasting apparatus described above is A die constructed in a cylindrical shape, A cylindrical member positioned above the die along the axis of the die, The system comprises a die and a cooler arranged to surround the cylindrical member, The distance between the die and the cylindrical member is 1.0 mm or more and 5.0 mm or less. A method for manufacturing oxygen-free copper wire.

4. The process includes a step for producing oxygen-free copper castings having a diameter of 15.6 mm or more and 16.4 mm or less using an upcasting apparatus. The upcasting apparatus described above is A die constructed in a cylindrical shape, A cylindrical member positioned above the die along the axis of the die, The system comprises a die and a cooler arranged to surround the cylindrical member, The distance between the die and the cylindrical member is 1.0 mm or more and 5.0 mm or less. A method for manufacturing oxygen-free copper castings.

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