Tungsten wire and fiber product

Abstract

This tungsten wire (1) has a resistivity value of 6.2 [mu] Omega * cm or more and 6.9 [mu] Omega * cm or less, a wire diameter of 50 [mu] m or less, and contains dislocations within crystal grains. For example, the tensile strength of the tungsten wire (1) is from 2200 MPa to 2800 MPa (inclusive).

Description

Technical Field

[0001] The invention relates to tungsten wire and fiber products. Background Art

[0002] Patent Document 1 discloses a metal fiber obtained by combining a tungsten wire having a roughened surface with an aromatic polyamide fiber or a nylon-based fiber.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-80413 Summary of the invention

[0006] Problems to be solved by the invention

[0007] Tungsten has a higher resistivity value and higher resistance than silver or copper. For example, in order to process tungsten into a wire and reduce resistance, the wire must be thickened. That is, conventional tungsten wires cannot have both low resistance and a thin wire diameter.

[0008] Therefore, an object of the present invention is to provide a tungsten wire and fiber product that can achieve both low resistance and a thin wire diameter.

[0009] Means for solving problems

[0010] The tungsten wire according to one embodiment of the present invention has a resistivity value of 6.2 μΩ·cm or more and 6.9 μΩ·cm or less, a wire diameter of 50 μm or less, and contains dislocations in crystal grains.

[0011] A fiber product according to one embodiment of the present invention is a fiber product including the tungsten wire according to the above embodiment.

[0012] Effects of the Invention

[0013] According to the present invention, a tungsten wire or the like that can achieve both low resistance and a thin wire diameter is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of tungsten wire and fiber products according to embodiments.

[0015] Figure 2 1 is a flowchart showing a method for producing a tungsten wire according to an embodiment.

[0016] Figure 3A This is a diagram showing an enlarged view of the surface of the tungsten wire of Example 1.

[0017] Figure 3B This is a diagram showing an enlarged view of the surface of the tungsten wire of Example 2.

[0018] Figure 3C This is a diagram showing an enlarged view of the surface of the tungsten wire of Example 3.

[0019] Figure 3D This is a diagram showing an enlarged view of the surface of the tungsten wire of Example 4.

[0020] Figure 3E This is a diagram showing an enlarged view of the surface of the tungsten wire of Example 5.

[0021] Figure 3F This is a diagram showing an enlarged view of the surface of the tungsten wire of Example 6.

[0022] Figure 4A This is a diagram showing an enlarged view of the surface of the tungsten wire of Comparative Example 1.

[0023] Figure 4B This is a diagram showing an enlarged view of the surface of the tungsten wire of Comparative Example 2.

[0024] Figure 4C This is a diagram showing an enlarged view of the surface of the tungsten wire of Comparative Example 3.

[0025] Figure 4D This is a diagram showing an enlarged view of the surface of the tungsten wire of Comparative Example 4.

[0026] Figure 4E This is a diagram showing an enlarged view of the surface of the tungsten wire of Comparative Example 5.

[0027] Figure 4F This is a diagram showing an enlarged view of the surface of the tungsten wire of Comparative Example 6.

[0028] Figure 5A The surface of the tungsten wire of Example 1 is Figure 3A A diagram showing an enlarged image at a high magnification.

[0029] Figure 5B The surface of the tungsten wire of Example 2 is Figure 3B A diagram showing an enlarged image at a high magnification.

[0030] Figure 5C The surface of the tungsten wire of Example 3 is Figure 3C A diagram showing an enlarged image at a high magnification.

[0031] Fig. 6A The surface of the tungsten wire of Comparative Example 2 is Figure 4B A diagram showing an enlarged image at a high magnification.

[0032] Figure 6B The surface of the tungsten wire of Comparative Example 3 is Figure 4C A diagram showing an enlarged image at a high magnification. DETAILED DESCRIPTION

[0033] Hereinafter, the tungsten wire and fiber products of the embodiments of the present invention are described in detail using the accompanying drawings. It should be noted that the embodiments described below are all embodiments representing a specific example of the present invention. Therefore, the numerical values, shapes, materials, components, configurations and connection forms of components, steps, and the order of steps shown in the following embodiments are examples, and the main purpose is not to limit the present invention. Therefore, the components not described in the independent claims among the components in the following embodiments are described as optional components.

[0034] In addition, each figure is a schematic diagram and may not be illustrated strictly. Therefore, for example, the scales in each figure may not be consistent. In addition, in each figure, the same symbols are marked for substantially the same structure, and repeated descriptions are omitted or simplified.

[0035] In the present specification, terms indicating the relationship between elements, terms indicating the shape of an element, and numerical ranges are not intended to have strict meanings but are intended to include substantially equivalent ranges, for example, differences of about several %.

[0036] (Implementation Method)

[0037] [constitute]

[0038] First, regarding the configuration of the tungsten wire and fiber product of this embodiment, Figure 1 Provide explanation. Figure 1 It is a schematic diagram showing the tungsten wire 1 and the fiber product according to the present embodiment.

[0039] like Figure 1 As shown in , the tungsten wire 1 is stored by being wound around a reel 2. The reel 2 is sometimes called a bobbin, a reel, a reel, or a drum. The tungsten wire 1 has a total length of, for example, about 100 m to a total length of a kilometer, but is not particularly limited.

[0040] Figure 1 The tungsten wire 1 shown in FIG. 1 can be processed twice. That is, the tungsten wire 1 is processed to form a part of a product. The product is, for example, a fiber product having one or more tungsten wires 1 of a predetermined length. The fiber product is a conductive fiber that utilizes the conductivity of the tungsten wire 1 .

[0041] Figure 1 , a twisted yarn 10 is shown as an example of a fiber product. The twisted yarn 10 includes a tungsten wire 1 and an organic fiber 11 combined with the tungsten wire 1.

[0042] The twisted yarn 10 is a core yarn having an organic fiber 11 as a core yarn and a tungsten wire 1 as a sheath yarn. For example, the twisted yarn 10 is manufactured by stretching and fixing the organic fiber 11 as a core yarn and winding the tungsten wire 1 as a sheath yarn around the organic fiber 11 (i.e., performing a covering process).

[0043] The tungsten wire 1 is wound along the outer side of the organic fiber 11 at a predetermined pitch. Figure 1 As shown in , the tungsten wire 1 has a gap between each roll, but adjacent rolls may be closely connected. The specific structure and manufacturing method of the tungsten wire 1 will be described below.

[0044] The organic fiber 11 is at least one fiber selected from the group consisting of synthetic fibers, natural fibers, and regenerated fibers. The organic fiber 11 is, for example, a synthetic fiber, such as an aromatic polyamide fiber, a nylon-based fiber, or a polyethylene-based fiber. As the aromatic polyamide fiber, for example, a fiber made of an aromatic polyamide-based resin material such as Kevlar (registered trademark) can be used. As the polyethylene-based fiber, for example, a fiber made of an ultra-high molecular weight polyethylene such as Dyneema (registered trademark) can be used.

[0045] It should be noted that the chemical fibers used as the organic fiber 11 are not limited to these, and polyester, polypropylene, polyurethane, polyvinyl chloride, acrylic acid, etc. can be used. Alternatively, the organic fiber 11 can also be a semi-synthetic fiber or a regenerated fiber. In addition, the organic fiber 11 can also be a natural fiber such as a plant fiber or an animal fiber. For example, cotton, wool, silk, hemp, rayon, etc. can be used as the organic fiber 11.

[0046] It should be noted that the twisted yarn 10 may be a core-covered yarn in which the core yarn is the tungsten wire 1 and the sheath yarn is the organic fiber 11. Alternatively, the twisted yarn 10 is not limited to the core-covered yarn, and may be a double-twisted yarn.

[0047] In addition, the twisted yarn 10 may not include the organic fiber 11, but include a plurality of tungsten wires 1. The twisted yarn 10 may also be manufactured by twisting a plurality of tungsten wires 1 (for example, coating or doubling). Alternatively, the twisted yarn 10 may be a twisted yarn of the tungsten wire 1 and other metal wires such as stainless steel wires.

[0048] also, Figure 1 In the figure, as an example of other fiber products, a net 20 is shown. The net 20 has a plurality of tungsten wires 1. The net 20 is manufactured by using a plurality of tungsten wires 1 as warp and weft and performing a weaving process. The fabric structure of the net 20 is not particularly limited to plain weave, twill weave, Dutch weave, satin weave, etc. The net 20 can also be manufactured by using a plurality of tungsten wires 1 as knitting yarns and performing a weaving process such as plain weave with a predetermined number of needles.

[0049] It should be noted that the net 20 may be manufactured by spinning or knitting using the twisted yarn 10. In addition, the net 20 may be three-dimensionally configured. For example, the net 20 may be configured as gloves, a hat, or clothes.

[0050] Since the fiber products such as the twisted yarn 10 and the net 20 have the conductive tungsten wire 1, they can be used for vital sign sensing, for example. For example, the fiber products can sense the body temperature or pulse of the wearer as an example of a vital sign. Specifically, the tungsten wire 1 of the fiber products functions as a terminal for sensing vital signs. That is, the tungsten wire 1 can detect the weak current generated by the wearer.

[0051] Alternatively, the fiber product may be provided with a terminal for sensing a vital sign separately. In this case, the tungsten wire 1 functions as a wiring for electrically connecting the terminal to a signal processing circuit.

[0052] Furthermore, the fiber product can also be used for heat generation. Specifically, a current can be passed through the tungsten wire 1 included in the fiber product to generate heat.

[0053] The fiber product may also be clothing items including gloves, clothes, headwear such as hats, socks, footwear such as tabards, etc. Alternatively, the fiber product may also be a towel, a handkerchief, a blanket, a bed sheet, etc.

[0054] In addition, the fiber product may be a nonwoven fabric produced by processing the tungsten wire 1 and the organic fiber 11 as wire materials. In addition, the fiber product may be a product obtained by gathering the tungsten wire 1 or the twisted yarn 10 into a cotton-like (cotton-like) shape. Alternatively, the fiber product may be a product obtained by sewing (embroidering or sewing) the tungsten wire 1 onto a fiber fabric such as a textile, a woven product, or a knitted product produced using organic fibers.

[0055] [Tungsten Wire]

[0056] Next, the specific structure of the tungsten wire 1 according to the present embodiment will be described.

[0057] The tungsten wire 1 is a metal wire containing tungsten (W) as a main component. The main component means that the content of the target element (here tungsten) is greater than 50wt%. For example, the tungsten content in the tungsten wire 1 is 90wt% or more. The tungsten content can also be 95wt% or more, 99wt% or more, or 99.9wt% or more. It should be noted that the tungsten content is the ratio of the weight of tungsten to the weight of the tungsten wire 1. The tungsten wire 1 can also be a pure tungsten wire with a content of substantially 100wt%. It should be noted that the pure tungsten wire may also contain unavoidable impurities that cannot be avoided in the manufacturing process.

[0058] The tungsten wire 1 may also be a tungsten alloy wire made of an alloy of tungsten and a metal element other than tungsten. Examples of metal elements other than tungsten include rhenium (Re), ruthenium (Ru), iridium (Ir), osmium (Os), and the like. For example, the content of metal elements such as rhenium constituting the alloy (solid solution) is greater than 0.1wt% and less than 10wt%, but is not limited thereto. The content of metal elements constituting the alloy may also be greater than 0.5wt% and less than 5wt%. As an example, the content of rhenium is 1wt%, but may also be 3wt%.

[0059] The tungsten wire 1 may be a doped tungsten wire doped with a predetermined element (doping element) such as potassium (K) or cerium (Ce). The content of the doping element is, for example, 0.005 wt % to 0.010 wt %, but is not limited thereto.

[0060] The wire diameter of the tungsten wire 1 is 50 μm or less. For example, the wire diameter of the tungsten wire 1 may be 40 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less. For example, the wire diameter of the tungsten wire 1 may be about 5 μm.

[0061] The tensile strength of the tungsten wire 1 is 2200 MPa or more and 2800 MPa or less. Thus, a tensile strength sufficient for use as a fiber product or the like can be ensured.

[0062] The average value of the width of the surface crystal grains in the direction perpendicular to the wire axis of the tungsten wire 1 is greater than 220 nm. The average value of the width of the surface crystal grains (hereinafter referred to as the average crystal width) is one of the parameters indicating the size of the crystal grains constituting the tungsten wire 1. The specific measurement method will be described later together with the examples. The average crystal width is, for example, greater than 220 nm and less than 310 nm.

[0063] The resistivity of the tungsten wire 1 is reduced by having an average crystal width of 220 nm or more. That is, the size of the crystal grains of the tungsten wire 1 is increased, so that the number of grain boundaries in the tungsten wire 1 is reduced. When current flows through the tungsten wire 1, the grain boundaries become obstacles to the movement of electrons, thereby generating resistance. In this embodiment, the resistivity of the tungsten wire 1 can be reduced by reducing the number of grain boundaries. Specifically, the resistivity of the tungsten wire 1 is greater than or equal to 6.2 μΩ·cm and less than or equal to 6.9 μΩ·cm.

[0064] Dislocations are contained in the crystal grains of the tungsten wire 1. Dislocations are linear crystal defects. Dislocations are generated in the wire drawing process (wire drawing process) in the method for manufacturing the tungsten wire 1. The generated dislocations are substantially (to a degree that cannot be observed at a predetermined magnification) disappeared when heated (annealed) at a predetermined temperature (e.g., 1200° C.) or higher. In other words, the tungsten wire 1 containing dislocations to a degree that can be observed at a predetermined magnification means that heating at a temperature or higher than the predetermined temperature is not performed after the final wire drawing process.

[0065] In addition, by including dislocations in the crystal grains of the tungsten wire 1, the secondary processability of the tungsten wire 1 is improved. For example, when the wire diameter is the same, the secondary processability of the tungsten wire 1 including dislocations is higher than that of the tungsten wire not including dislocations. Specifically, the flexibility (bendability) of the tungsten wire 1 including dislocations is increased, and secondary processes such as twisting, weaving, and netting using the tungsten wire 1 that involve bending or curving can be performed. This is because the propagation of the force applied to the tungsten wire 1 during the secondary processing is suppressed by the dislocations in the crystal grains, and the occurrence of wire breakage of the tungsten wire 1 can be suppressed.

[0066] It should be noted that dislocations do not occur to the extent that they produce elastic deformation. Figure 1 As shown in , no dislocation occurs to the extent that the tungsten wire 1 is wound around the reel 2 for storage.

[0067] As described above, the tungsten wire 1 of the present embodiment can achieve both low resistance and a thin wire diameter. In addition, the tungsten wire 1 of the present embodiment can be subjected to secondary processing such as twisting processing, and the above-mentioned fiber products can be manufactured.

[0068] [Manufacturing method]

[0069] Next, the method for manufacturing the tungsten wire 1 of the present embodiment uses Figure 2 Provide explanation. Figure 2 1 is a flowchart showing a method for producing the tungsten wire 1 according to the present embodiment.

[0070] First, if Figure 2 As shown in , a tungsten wire having a predetermined wire diameter (e.g., about 3 mm) thicker than the final target wire diameter is drawn at a high degree of processing (S10). The tungsten wire of the predetermined wire diameter is produced by repeatedly performing upsetting or rolling processing on a tungsten ingot. In addition, the tungsten ingot is produced by preparing an aggregate of tungsten powder and pressing and sintering the prepared aggregate. It should be noted that by mixing a powder of an alloy element or a powder of a doping element in the tungsten powder, a tungsten alloy wire or a doped tungsten wire can be produced.

[0071] The processing degree is the cross-sectional reduction rate caused by wire drawing. Specifically, the processing degree is a value obtained by subtracting the ratio of the cross-sectional area of ​​the tungsten wire after wire drawing to the cross-sectional area of ​​the tungsten wire before wire drawing from 1 as a percentage. The higher the processing degree, the greater the reduction in cross-sectional area caused by wire drawing, and the lower the processing degree, the less the reduction in cross-sectional area caused by wire drawing. That is, for tungsten wire of the same wire diameter, the wire diameter of the tungsten wire after wire drawing with a high processing degree becomes thinner than the wire diameter of the tungsten wire after wire drawing with a low processing degree.

[0072] In step S10 , the high working degree is specifically a working degree of 80% or more. For example, wire drawing is performed at a working degree of 80% or more and 95% or less.

[0073] Wire drawing is performed using one or more wire drawing dies. In the wire drawing process, a lubricant obtained by dispersing graphite in water may also be used. It should be noted that the tungsten wire may also be annealed before the initial wire drawing. By annealing, an oxide layer is formed on the surface of the tungsten wire. This can suppress the occurrence of wire breakage during the wire drawing process.

[0074] When the next wire drawing is not the last wire drawing (No in S12), the tungsten wire is annealed (S14). By performing annealing, the deterioration of the workability of the wire drawing can be suppressed. The annealing temperature is, for example, a temperature above 1000°C and below 1600°C, but is not limited to this. After annealing, return to step S10 and perform wire drawing with a high degree of processing. By repeatedly performing wire drawing (S10) and annealing (S14), the tungsten wire is reduced in diameter until the desired wire diameter. During the repeated wire drawing, electrolytic grinding can also be performed in the middle. Electrolytic grinding can make the surface of the tungsten wire smooth, which can improve the workability and suppress the occurrence of wire breakage during wire drawing.

[0075] When the next wire drawing is the final wire drawing (Yes in S12), the tungsten wire is annealed (S16). The annealing temperature is 1200°C or higher and 1600°C or lower. The annealing temperature is, for example, higher than the temperature of the previous annealing (S14), but is not limited thereto.

[0076] Next, the tungsten wire after annealing (S16) is drawn at a low processing degree (S18). The low processing degree here is a processing degree lower than the processing degree in step S10. Specifically, the so-called low processing degree is greater than 20% and less than 50%. For example, wire drawing is performed at a processing degree of about 30%. In the final wire drawing of step S18, dislocations are formed in the crystal grains of the tungsten wire. It should be noted that in the processes after step S18, annealing at a temperature above 1200°C is not performed.

[0077] When the working degree in the final wire drawing is greater than 50%, the crystal grains become smaller and the resistivity value cannot be reduced. When the working degree in the final wire drawing is less than 20%, dislocations are not formed in the crystal grains and the secondary workability of the tungsten wire 1 cannot be sufficiently improved.

[0078] Finally, the drawn tungsten wire is electrolytically polished (S20). Electrolytic polishing is performed, for example, by immersing the tungsten wire and the counter electrode in an electrolyte such as sodium hydroxide aqueous solution to generate a potential difference between the tungsten wire and the counter electrode. Through electrolytic polishing, the wire diameter of the tungsten wire is slightly reduced and adjusted to the desired wire diameter. It should be noted that electrolytic polishing (S20) may not be performed.

[0079] Through the above steps, the above-mentioned tungsten wire 1 can be manufactured.

[0080] In addition, each process shown in the manufacturing method of the tungsten wire 1 is performed online, for example. Specifically, the multiple wire drawing dies used in step S10 are arranged on the production line in the order of decreasing aperture diameter. In addition, a heating device such as a burner is arranged between each wire drawing die. In addition, an electrolytic grinding device may also be arranged between each wire drawing die. On the downstream side (post-process side) of the wire drawing die used in step S10, one or more wire drawing dies used in step S18 are arranged in the order of decreasing aperture diameter, and an electrolytic grinding device is arranged on the downstream side of the wire drawing die with the smallest aperture diameter. It should be noted that each process may also be performed individually.

[0081] [Examples and Comparative Examples]

[0082] Next, specific examples and comparative examples of the tungsten wire 1 according to the present embodiment will be described.

[0083] The tungsten wires of Examples 1 to 3 and Comparative Examples 1 to 3 have a wire diameter of 24 μm. The tungsten wires of Examples 4 to 6 and Comparative Examples 4 to 6 have a wire diameter of 48 μm. It should be noted that the tungsten content of Examples 1 to 6 and Comparative Examples 1 to 6 is 99.9 wt % or more.

[0084] The tungsten wire of the embodiment is made according to Figure 2 The tungsten wire of the comparative example is replaced by the tungsten wire of the comparative example. Figure 2 The tungsten wire that is drawn with a low degree of processing in step S18 of the manufacturing method shown in , or the tungsten wire that is annealed after the drawing. The specific manufacturing methods of each embodiment and each comparative example are as follows. It should be noted that the processing methods of embodiments 1 to 6 and comparative examples 1 to 6 until the wire diameter becomes 180 μm are the same.

[0085] <Example 1>

[0086] In Example 1, a tungsten wire with a wire diameter of 180 μm was annealed at 1500°C (S14), and then drawn at a processing degree of 80% (S12, the first two drawing times before the final drawing) to produce a tungsten wire with a wire diameter of 80 μm. Next, after annealing at 1100°C (S14), the wire was drawn at a processing degree of 86% (S12, the first drawing time before the final drawing) to produce a tungsten wire with a wire diameter of 30 μm. Next, after annealing at 1200°C (S16), the wire was drawn at a processing degree of 30% (S18) to produce a tungsten wire with a wire diameter of 25.1 μm. Thereafter, electrolytic polishing (S20) was performed to produce the tungsten wire of Example 1 with a wire diameter of 24 μm.

[0087] <Example 2>

[0088] Example 2 is a production method substantially the same as that of Example 1, except that annealing before the final wire drawing in step S16 is performed at 1400°C.

[0089] <Example 3>

[0090] Example 3 is a production method substantially the same as that of Example 1, except that annealing before the final wire drawing in step S16 is performed at 1600°C.

[0091] <Example 4>

[0092] In Example 4, a tungsten wire with a wire diameter of 180 μm was annealed at 1500°C (S14), and then drawn at a processing degree of 90% (S12, the first drawing before the final drawing) to produce a tungsten wire with a wire diameter of 57 μm. Next, after annealing at 1200°C (S16), the wire was drawn at a processing degree of 23% (S18) to produce a tungsten wire with a wire diameter of 50 μm. Thereafter, electrolytic polishing (S20) was performed to produce the tungsten wire of Example 4 with a wire diameter of 48 μm.

[0093] <Example 5>

[0094] Example 5 is a production method substantially the same as that of Example 4, except that annealing before the final wire drawing in step S16 is performed at 1400°C.

[0095] <Example 6>

[0096] Example 6 is a production method substantially the same as that of Example 4, except that annealing before the final wire drawing in step S16 is performed at 1600°C.

[0097] <Comparative Example 1>

[0098] In Comparative Example 1, a tungsten wire having a wire diameter of 180 μm is annealed at 1500°C and then drawn at a processing degree of 80% (the last drawing before the final drawing) to produce a tungsten wire having a wire diameter of 80 μm. Next, after annealing at 1100°C, the wire is drawn at a processing degree of 91% (the final drawing) to produce a tungsten wire having a wire diameter of 25.1 μm. Thereafter, electrolytic polishing (S20) is performed to produce the tungsten wire of Comparative Example 1 having a wire diameter of 24 μm. Comparative Example 1 corresponds to the case where the processing degree is high in the final drawing step (S18) in the manufacturing method of the present application.

[0099] <Comparative Example 2>

[0100] In Comparative Example 2, the tungsten wire manufactured by the same manufacturing method as that of Comparative Example 1 was annealed at 1400° C. after the final wire drawing.

[0101] <Comparative Example 3>

[0102] In Comparative Example 3, the tungsten wire manufactured by the same manufacturing method as that of Comparative Example 1 was annealed at 1600° C. after the final wire drawing.

[0103] <Comparative Example 4>

[0104] In Comparative Example 4, a tungsten wire having a wire diameter of 180 μm was annealed at 1500°C and then drawn at a processing degree of 94% (final drawing) to produce a tungsten wire having a wire diameter of 50 μm. Thereafter, electrolytic polishing (S20) was performed to produce a tungsten wire of Comparative Example 4 having a wire diameter of 48 μm. Comparative Example 4 corresponds to a case where the processing degree is high in the final drawing step (S18) in the manufacturing method of the present application.

[0105] <Comparative Example 5>

[0106] In Comparative Example 5, the tungsten wire manufactured by the same manufacturing method as that of Comparative Example 4 was annealed at 1400° C. after the final wire drawing.

[0107] <Comparative Example 6>

[0108] In Comparative Example 6, the tungsten wire manufactured by the same manufacturing method as that of Comparative Example 4 was annealed at 1600° C. after the final wire drawing.

[0109] [Evaluation results]

[0110] Next, the resistivity, tensile strength, average crystal width and secondary processability of the tungsten wires of Examples 1 to 6 and Comparative Examples 1 to 6 were measured and evaluated, and the results are shown in Tables 1 and 2, and Figure 3A to Figure 6B Regarding Examples 1 to 3 and Comparative Examples 2 and 3, the presence or absence of dislocation was also evaluated.

[0111] Figure 3A to Figure 3F These are diagrams showing enlarged views of the surfaces of the tungsten wires of Examples 1 to 6, respectively. Figure 4A to Figure 4F The figures are magnified surfaces of tungsten wires of Comparative Examples 1 to 6. Each figure shows a SEM (Scanning Electron Microscope) image of the surface of the manufactured tungsten wire. In each figure, the same shade (color) range represents one crystal grain. The left-right direction of the paper of each figure is parallel to the axis of the tungsten wire, and the surface crystal grains extend in a long strip along the axis.

[0112] In each figure, the solid line L drawn vertically near the center is a straight line extending in a direction perpendicular to the line axis. The average value of the width of the surface crystal grains, i.e., the average crystal width, is calculated by counting the number of the boundary (i.e., grain boundary) of the crystal grains and the crystal grains along the solid line L within the range shown in each figure. Specifically, by dividing the length of the counting range, i.e., the length of the longitudinal direction of each figure by the grain boundary number + 1, the average value of the width of the surface crystal grains is calculated. It should be noted that in each figure, a plurality of short line segments orthogonal to the solid line L represent the position of the grain boundary respectively.

[0113] Figure 5A to Figure 5C The surfaces of the tungsten wires of Examples 1 to 3 were Figure 3A to Figure 3C A diagram showing an enlarged image at a high magnification. Fig. 6A and Figure 6B The surfaces of the tungsten wires of Comparative Examples 2 and 3 were Figure 4B and Figure 4C A diagram showing an enlarged image at a high magnification.

[0114] exist Figure 5A to Figure 5C In each figure, the range of dislocations confirmed to be contained in the crystal grains is surrounded by a solid line frame. In each figure, the bumps and depressions that appear slightly in a manner that intersects the wire axis direction of the tungsten wire (the left and right direction of the paper in the figure) correspond to dislocations. It is known that dislocations appear in any of Examples 1 to 3. It should be noted that, although not shown in the figure, Examples 4 to 6, which differ only in wire diameter from Examples 1 to 3, are also manufactured by the same manufacturing method as Examples 1 to 3, so it is presumed that dislocations are contained in the crystal grains.

[0115] On the other hand, Fig. 6A and Figure 6B As shown in FIG. 1 , in Comparative Examples 2 and 3, which were annealed after the final wire drawing, the Figure 5A to Figure 5C It is assumed that the dislocations disappear due to recrystallization of crystal grains during annealing after wire drawing.

[0116] Table 1 shows the evaluation results of the tungsten wires of Examples 1 to 3 and Comparative Examples 1 to 3 (wire diameter: 24 μm). Table 2 shows the evaluation results of the tungsten wires of Examples 4 to 6 and Comparative Examples 4 to 6 (wire diameter: 48 μm).

[0117] Table 1

[0118]

[0119] Table 2

[0120]

[0121] As shown in Table 1, the tungsten wires of Examples 1 to 3 have lower resistivity values ​​than the tungsten wire of Comparative Example 1. Specifically, the resistivity improvement rates of Examples 1 to 3 are 5.6%, 9.6%, and 12.6%, respectively. It should be noted that the resistivity improvement rate is a value expressed as a percentage of 1 minus the ratio of the resistivity value of the tungsten wire of each Example to the resistivity value of the tungsten wire of Comparative Example 1. It is found that the higher the temperature of the final annealing (S16) (for example, Comparative Example 3 compared to Comparative Example 1), the lower the resistivity becomes and the higher the improvement rate becomes.

[0122] The tungsten wires of Comparative Examples 2 and 3 achieved resistivity values ​​equivalent to those of Examples 1 to 3. This is presumably because the annealing performed after the final wire drawing caused the enlargement of the crystal grains caused by recrystallization. The average crystal width has a correlation with the resistivity value and the tensile strength. The larger the average crystal width, the lower the resistivity value and the lower the tensile strength. The smaller the average crystal width, the higher the resistivity value and the higher the tensile strength.

[0123] However, although comparative examples 2 and 3 achieved the same resistivity values ​​as those of examples 1 to 3, the secondary processability was low. This is presumably because: Fig. 6A and Figure 6B As shown in , no dislocations are contained in the crystal grains.

[0124] It should be noted that in Table 1 and Table 2, "Secondary Processing" indicates whether or not the secondary processing of the tungsten wire of each embodiment or each comparative example is possible. Specifically, as the secondary processing, a twisting process using the tungsten wire is performed. The twisting process is a predetermined twisting process performed on the target tungsten wire. Specifically, the bending process is performed with a curvature radius equal to the diameter of the target tungsten wire.

[0125] In Tables 1 and 2, "Not possible" means that the tungsten wire broke during the yarn twisting process and the yarn twisting process was not performed. "Permitted" means that the tungsten wire did not break and the yarn twisting process was performed.

[0126] The tungsten wires of Examples 1 to 3 can all be processed twice. It is presumed that this is because, as described above, dislocations are contained in the crystal grains. The tungsten wire of Comparative Example 1 can also be processed twice as in the Examples. However, the tungsten wire of Comparative Example 1 has a high resistivity value as described above. That is, Comparative Example 1 cannot achieve a low resistivity value and high secondary processability.

[0127] On the other hand, although the resistivity values ​​of Comparative Examples 2 and 3 were low, secondary processing could not be performed. Specifically, when the above-mentioned twisting process was performed, the tungsten wire was brittle and wire breakage occurred. That is, for Comparative Examples 2 and 3, low resistivity values ​​and high secondary processability could not be achieved.

[0128] As described above, regarding the tungsten wire having a wire diameter of 24 μm, Examples 1 to 3 can achieve both low resistivity and high secondary processability, whereas Comparative Examples 1 to 3 cannot achieve both low resistivity and high secondary processability.

[0129] In addition, regarding the tensile strength, the tungsten wires of Examples 1 to 3 have lower tensile strength than the tungsten wire of Comparative Example 1. Although the tensile strength is reduced, a tensile strength sufficient for use as a fiber product or the like can be ensured.

[0130] Furthermore, as shown in Table 2, the tungsten wires of Examples 4 to 6 having larger wire diameters than Examples 1 to 3 showed the same tendency as that of Examples 1 to 3. Specifically, the tungsten wires of Examples 4 to 6 had lower resistivity values ​​than the tungsten wire of Comparative Example 4. More specifically, the resistivity improvement rates of Examples 4 to 6 were 5.2%, 10.5%, and 12.6%, respectively.

[0131] The tensile strength, average crystal width and secondary processability of Examples 4 to 6 also showed the same tendency as that of Examples 1 to 3. That is, it was found that the use of the tungsten wire of each Example could achieve both low resistivity and high secondary processability regardless of the wire diameter.

[0132] As described above, the tungsten wire 1 of the present embodiment is annealed before the final wire drawing and then final wire drawing is performed at a low degree of processing, thereby obtaining a tungsten wire 1 that achieves a thin wire diameter, a low resistivity value, and high secondary processability.

[0133] (Summary)

[0134] The tungsten wire according to the first aspect of the present invention is, for example, the above-mentioned tungsten wire 1 , has a resistivity value of 6.2 μΩ·cm or more and 6.9 μΩ·cm or less, has a wire diameter of 50 μm or less, and contains dislocations in crystal grains.

[0135] Thus, it is possible to achieve both low resistance and thin wire diameter. By reducing the resistivity value, it is possible to achieve a resistance equivalent to that of a thick tungsten wire with a thin tungsten wire 1 (specifically, a reduction in cross-sectional area of ​​about 5% to 13%). It should be noted that the ratio of the reduction in cross-sectional area corresponds to the above-mentioned resistivity improvement rate.

[0136] Furthermore, the tungsten wire of the first aspect can achieve high secondary workability by including dislocations in crystal grains. That is, the tungsten wire of the first aspect can be used for secondary processing into various products.

[0137] Furthermore, the tungsten wire according to a second aspect of the present invention is the tungsten wire according to the first aspect, and has a tensile strength of 2200 MPa to 2800 MPa.

[0138] Thereby, sufficient tensile strength for use as a fiber product or the like can be ensured.

[0139] Furthermore, the tungsten wire according to the third aspect of the present invention is the tungsten wire according to the first aspect or the second aspect, wherein the average value of the width of surface crystal grains of the tungsten wire in a direction perpendicular to the wire axis is 220 nm or more.

[0140] Thereby, a low resistivity value can be achieved.

[0141] A fiber product according to a fourth aspect of the present invention comprises the tungsten wire according to any one of the first to third aspects.

[0142] Therefore, since the resistivity of tungsten wire is low, the fiber product can be used for vital sign sensing using the conductivity of tungsten wire. In addition, the thin wire diameter of tungsten wire is useful for fiber products that are directly used by people such as clothing and towels. For example, if the wire diameter is thick, the skin feel becomes worse, while in contrast, since the wire diameter of the tungsten wire of this embodiment is thin, a fiber product with good skin feel can be realized.

[0143] Furthermore, a fiber product according to a fifth aspect of the present invention is the fiber product according to the fourth aspect, and is the twisted yarn 10 or the web 20 .

[0144] Therefore, it can be applied to various clothing products and the like.

[0145] (other)

[0146] As mentioned above, the tungsten wire and the fiber product of the present invention have been described based on the above-mentioned embodiments and the like, but the present invention is not limited to the above-mentioned embodiments.

[0147] For example, the example in which the tungsten wire is processed twice to produce a fiber product is shown, but the invention is not limited thereto. The tungsten wire can also be used as an electrode for electric discharge machining, for example.

[0148] In addition, the present invention also includes the following methods: methods obtained by implementing various modifications that can be conceived by those skilled in the art to the various embodiments; methods achieved by arbitrarily combining the constituent elements and functions in the various embodiments without departing from the gist of the present invention.

[0149] Explanation of symbols

[0150] 1 Tungsten wire

[0151] 10 twist yarn (fiber products)

[0152] 20 net (fiber products)

Claims

1. A tungsten wire having a resistivity value of 6.2 μΩ·cm or more and 6.9 μΩ·cm or less, The wire diameter is less than 50μm. Dislocations are contained within the grains. 2 . The tungsten wire according to claim 1 , wherein the tensile strength is 2200 MPa or more and 2800 MPa or less.

3. The tungsten wire according to claim 1 or 2, wherein: The average value of the width of surface crystal grains of the tungsten wire in a direction perpendicular to the wire axis is 220 nm or more. A fiber product comprising the tungsten wire according to claim 1 or 2.

5. The fiber product according to claim 4, wherein: The fiber product is twisted yarn or net.

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