TWI901970B - Tungsten wire and fiber products - Google Patents

Abstract

The present invention provides a tungsten wire and fiber product. The tungsten wire (1) of the present invention has a specific resistance of 6.2 μΩ·cm or more and 6.9 μΩ·cm or less; a wire diameter of 50 μm or less; and contains differential packing within the grains. For example, the tensile strength of the tungsten wire (1) is 2200 MPa or more and 2800 MPa or less.

Description

Tungsten wire and fiber products

This invention relates to a tungsten wire and fiber product.

Patent document 1 discloses a metal fiber composed of surface-roughened tungsten wire combined with aromatic polyamide fibers or nylon-based fibers.

[Learning Technology Literature] [Patent Documents]

Patent Document 1: Japanese Patent Application Publication No. 2018-80413

Tungsten has a higher resistivity than silver or copper. For example, to process tungsten into wires (leads) and reduce resistance, the wire must be thicker. In other words, conventional tungsten wire cannot simultaneously achieve low resistance and a thin wire diameter.

Therefore, the purpose of this invention is to provide a tungsten wire and fiber product that combines low resistance and fine wire diameter.

The tungsten wire of this invention has a specific resistivity of 6.2 μΩ·cm or higher and 6.9 μΩ·cm or lower; a wire diameter of 50 μm or lower; and contains dislocations within the grains.

The fiber product of this invention is a fiber product comprising the aforementioned tungsten yarn in one state.

According to this invention, tungsten wires that can balance low resistance and fine wire diameter are provided.

1: Tungsten wire

2: Winding spool

10: Twisted yarn (fiber products)

11: Organic Fibers

20: Mesh (fiber products)

Figure 1 is a schematic diagram of tungsten wire and fiber products in their actual form.

Figure 2 is a flowchart illustrating the manufacturing method of tungsten wire in an embodiment.

Figure 3A is a magnified view of the surface of the tungsten wire in Embodiment 1.

Figure 3B is a magnified view of the surface of the tungsten wire in Embodiment 2.

Figure 3C is a magnified view of the surface of the tungsten wire in Embodiment 3.

Figure 3D is a magnified view of the surface of the tungsten wire in Embodiment 4.

Figure 3E is a magnified view of the surface of the tungsten wire in Embodiment 5.

Figure 3F is a magnified view of the surface of the tungsten wire in Embodiment 6.

Figure 4A is a magnified view of the surface of the tungsten wire in Comparative Example 1.

Figure 4B is a magnified view of the surface of the tungsten wire in Comparative Example 2.

Figure 4C is a magnified view of the surface of the tungsten wire in Comparative Example 3.

Figure 4D is a magnified view of the surface of the tungsten wire in Comparative Example 4.

Figure 4E is a magnified view of the surface of the tungsten wire in Comparative Example 5.

Figure 4F is a magnified view of the surface of the tungsten wire in Comparative Example 6.

Figure 5A is a magnified view of the surface of the tungsten wire in Embodiment 1 at a higher magnification than Figure 3A.

Figure 5B is a magnified view of the surface of the tungsten wire in Embodiment 2 at a higher magnification than Figure 3B.

Figure 5C is a magnified view of the surface of the tungsten wire in Embodiment 3 at a higher magnification than Figure 3C.

Figure 6A is a magnified view of the tungsten wire surface of Comparative Example 2 at a higher magnification than Figure 4B.

Figure 6B is a magnified view of the tungsten wire surface of Comparative Example 3 at a higher magnification than Figure 4C.

The following describes in detail, using drawings, tungsten wire and fiber products according to embodiments of the present invention. Furthermore, the embodiments described below are merely specific examples of the present invention. Therefore, the values, shapes, materials, constituent elements, arrangements and connections of constituent elements, steps, and sequences of steps shown in the following embodiments are all examples and are not intended to limit the present invention. Therefore, constituent elements not described in the independent claims of the constituent elements of the following embodiments will be described as arbitrary constituent elements.

Furthermore, all diagrams are schematic and not drawn in a rigorous manner. Therefore, for example, the scale does not necessarily have to be consistent across diagrams. Additionally, substantially identical components are given the same symbols across diagrams, and redundant explanations are omitted or simplified.

Furthermore, in this specification, the terms used to indicate relationships between elements, the terms used to describe the shape of elements, and the range of values do not refer to a strict definition, but rather to substantially equivalent ranges, including, for example, variations of a few percent.

(Implementation Form)

[composition]

First, Figure 1 will be used to explain the tungsten wire and fiber products of this embodiment. Figure 1 is a schematic diagram of the tungsten wire 1 and fiber products of this embodiment.

As shown in Figure 1, tungsten wire 1 is wound and stored on a spool 2. The spool 2 may be called a drum, reel, coil, or roller, etc. The tungsten wire 1 may have a total length ranging from meters (100m) to kilometers (kilometers), but is not specifically limited to this.

The tungsten wire 1 shown in Figure 1 can undergo secondary processing. That is, the tungsten wire 1 can be processed to become part of a product. The product, for example, is a fiber product having one or more tungsten wires 1 of a predetermined length. The fiber product is a conductive fiber utilizing the electrical conductivity of the tungsten wire 1.

Figure 1 shows a strand 10 as an example of a fiber product. The strand 10 comprises tungsten wire 1 and organic fibers 11 combined with the tungsten wire 1.

The twisted wire 10 is a coated wire, with organic fiber 11 as the core and tungsten wire 1 as the sheath. For example, the organic fiber 11 is extended and fixed as the core, and tungsten wire 1 is wound around the organic fiber 11 as the sheath (i.e., a coating process is performed) to manufacture the twisted wire 10.

Tungsten wire 1 is wound along the outer surface of organic fiber 11 at predetermined intervals. As shown in Figure 1, the tungsten wire 1 is wound with intervals between each winding, but adjacent windings can also be made close together. The specific structure and manufacturing method of tungsten wire 1 will be explained later.

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

Furthermore, the chemical fibers used as organic fiber 11 are not limited to these; polyester, polypropylene, polyurethane, polyvinyl chloride, acrylate, etc., may also be used. Alternatively, organic fiber 11 may also be a semi-synthetic fiber or a regenerated fiber. In addition, organic fiber 11 may also be a natural fiber such as plant fiber or animal fiber. For example, cotton, wool, silk, hemp, rayon, etc., can be used as organic fiber 11.

Alternatively, the twisted wire 10 can also be a sheathed wire in which the core wire is tungsten wire 1 and the sheath wire is an organic fiber 11. Or, the twisted wire 10 is not limited to a sheathed wire and can also be a twisted wire.

Furthermore, the strand 10 may also consist of a plurality of tungsten wires 1 but without organic fibers 11. The strand 10 may also be manufactured by twisting a plurality of tungsten wires 1 (e.g., coating or twisting). Alternatively, the strand 10 may also be a strand of tungsten wires 1 and other metal wires such as stainless steel wire.

Furthermore, Figure 1 shows a mesh 20 as an example of another fiber product. The mesh 20 has a plurality of tungsten threads 1. The mesh 20 is manufactured by weaving the plurality of tungsten threads 1 as warp and weft threads. The weave structure of the mesh 20 is not particularly limited to plain weave, yarn weave, quilted weave, or satin weave, etc. The mesh 20 can also be manufactured by using the plurality of tungsten threads 1 as knitting threads to perform knitting processes such as plain knit with a predetermined number of stitches.

Furthermore, the mesh 20 can be manufactured using woven or knitted processes with the twisted yarn 10. Additionally, the mesh 20 can also be three-dimensionally constructed. For example, the mesh 20 can also be used to make gloves, hats, or clothing.

Fiber products such as twisted strands 10 or mesh 20, containing conductive tungsten wires 1, can be used for applications such as vital sign monitoring. For example, fiber products, as a form of vital sign monitoring, can monitor the wearer's body temperature or pulse. Specifically, the tungsten wires 1 in the fiber product function as terminals for vital sign monitoring. That is, the tungsten wires 1 can detect the weak current emitted by the wearer.

Alternatively, fiber products can also be equipped with terminals for monitoring vital signs. In this case, tungsten wire 1 functions as a wiring connection to electrically connect the terminal to the signal processing circuit.

In addition, fiber products can also be used for heating applications. Specifically, current can be circulated through the tungsten wires 1 within the fiber product to generate heat.

Fiber products can also include gloves, clothing, hats, and footwear such as socks and split-toe socks. Alternatively, fiber products can also include towels, hand towels, handkerchiefs, blankets, and bed sheets.

Furthermore, the fiber product can also be a nonwoven fabric manufactured by using tungsten thread 1 and organic fiber 11 as separate threads for nonwoven processing. Additionally, the fiber product can also be a cotton-like substance formed by combining tungsten thread 1 or twisted thread 10. Alternatively, the fiber product can also be a product in which tungsten thread 1 is used for post-sewing (embroidery or stitching) of woven, knitted, or braided fabrics made from organic fibers.

[Tungsten wire]

Next, the specific structure of tungsten wire 1 in this embodiment will be explained.

Tungsten wire 1 is a metal wire in which tungsten (W) is included as the main component. The main component refers to the content of the target element (tungsten in this case) exceeding 50 wt%. For example, the tungsten content in tungsten wire 1 is 90 wt% or more. The tungsten content can also be 95 wt% or more, 99 wt% or more, or 99.9 wt% or more. Furthermore, the tungsten content is the ratio of the weight of tungsten to the weight of tungsten wire 1. Tungsten wire 1 can also be pure tungsten wire with a substantial tungsten content of 100 wt%. Additionally, pure tungsten wire may contain unavoidable impurities that cannot be prevented from being introduced during the manufacturing process.

Tungsten wire 1 can also be a tungsten alloy wire formed from tungsten and alloys of other metallic elements. Examples of metallic elements other than tungsten include ruthenium (Re), chromium (Ru), iridium (Ir), and titanium (Os). For example, the content of the metallic element constituting the alloy (solid solution) of ruthenium, etc., is between 0.1 wt% and 10 wt%, but is not limited to this form. The content of the metallic element constituting the alloy can also be between 0.5 wt% and 5 wt%. As an example, the ruthenium content can be 1 wt%, or it can be 3 wt%.

Furthermore, tungsten line 1 can also be a doped tungsten line doped with predetermined elements such as potassium (K) and cerium (Ce). The content of the dopant element is, for example, 0.005 wt% to 0.010 wt%, but is not limited to this form.

The diameter of tungsten wire 1 is 50 μm or less. For example, the diameter of tungsten wire 1 can also be 40 μm or less, 30 μm or less, 20 μm or less, or 10 μm or less. For example, the diameter of tungsten wire 1 can even be around 5 μm.

The tensile strength of tungsten wire 1 is above 2200 MPa and below 2800 MPa. This ensures sufficient tensile strength for its use in fiber products.

The average width of the surface grains of tungsten wire 1 in the direction perpendicular to the wire axis is 220 nm or more. The average width of the surface grains (hereinafter referred to as the average grain width) is one parameter representing the size of the grains constituting tungsten wire 1. Specific measurement methods will be described later along with embodiments. The average grain width is, for example, 220 nm or more and 310 nm or less.

By increasing the average crystal width to 220 nm or more, the specific resistance of tungsten wire 1 is reduced. That is, by increasing the size of the grains in tungsten wire 1, the number of grain boundaries within tungsten wire 1 is reduced. When current flows through tungsten wire 1, resistance is generated because the grain boundaries impede the movement of electrons. In this embodiment, by reducing the number of grain boundaries, the specific resistance of tungsten wire 1 is reduced. Specifically, the specific resistance of tungsten wire 1 is 6.2 μΩ·cm or more and 6.9 μΩ·cm or less.

The tungsten wire 1 contains dislocations within its grains. Dislocations are linear crystalline defects. These dislocations occur during the wire drawing step (stretching step) of the tungsten wire 1 manufacturing method. The dislocations that occur are substantially eliminated (to a degree that is not observable at a given magnification) when heated (annealed) at a predetermined temperature (e.g., 1200°C). In other words, tungsten wire 1 containing dislocations to a degree observable at a given magnification refers to tungsten wire 1 where heating above the aforementioned predetermined temperature was not performed after the final wire drawing step.

Furthermore, by incorporating differential packing within the grains of the tungsten wire 1, its secondary processing capability is improved. For example, when comparing wire diameters, the secondary processing capability of the tungsten wire 1 containing differential packing is higher than that of the tungsten wire without differential packing. Specifically, the increased flexibility (bending) of the tungsten wire 1, including differential packing, allows for secondary processing involving bending or folding, such as twisting, weaving, and web formation. This is because the force transmission applied to the tungsten wire 1 during secondary processing is suppressed by the differential packing within the grains, thus preventing wire breakage.

Furthermore, misalignment did not occur to the extent that it caused elastic deformation. For example, misalignment did not occur when the tungsten wire 1 was wound around the spool 2 for storage, as shown in Figure 1.

As described above, the tungsten wire 1 of this embodiment achieves both low resistance and fine wire diameter. Furthermore, the tungsten wire 1 of this embodiment can undergo secondary processing such as stranding to manufacture the aforementioned fiber products.

[Manufacturing Method]

Next, the manufacturing method of the tungsten wire 1 of this embodiment will be explained using Figure 2. Figure 2 is a flowchart showing the manufacturing method of the tungsten wire 1 of this embodiment.

First, as shown in Figure 2, tungsten wire with a predetermined wire diameter (e.g., approximately 3 mm) that is thicker than the final target wire diameter is drawn with a high degree of workability (S10). Tungsten wire with the predetermined wire diameter is manufactured by repeatedly forging or rolling tungsten ingots. Furthermore, tungsten ingots are manufactured by pressing and sintering a prepared aggregate of tungsten powder. Additionally, tungsten alloy wire or doped tungsten wire can be manufactured by mixing powders of alloying elements or dopant elements into tungsten powder.

The degree of finishing refers to the reduction in cross-sectional area resulting from wire drawing. Specifically, the degree of finishing is expressed as a percentage, representing the ratio of the cross-sectional area of the tungsten wire after drawing (subtracting the cross-sectional area from 1) to the cross-sectional area of the tungsten wire before drawing. A higher degree of finishing results in a greater reduction in cross-sectional area; a lower degree of finishing results in a smaller reduction. In other words, for tungsten wire of the same diameter, wire drawn with a higher degree of finishing will have a thinner diameter than wire drawn with a lower degree of finishing.

In step S10, a high degree of machining is specified, specifically 80% or higher. For example, wire drawing is performed with a machining degree of 80% to 95%.

Wire drawing is performed using one or more drawing dies. A lubricant consisting of graphite dispersed in water can also be used during the wire drawing process. Alternatively, the tungsten wire can be annealed before the initial wire drawing. Annealing forms an oxide layer on the surface of the tungsten wire, thereby suppressing wire breakage during the wire drawing process.

If the next wire drawing is not the final drawing (not in S12), the tungsten wire is annealed (S14). Annealing helps to suppress the deterioration of the wire's workability. The annealing temperature is, for example, 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 workability. By repeating wire drawing (S10) and annealing (S14), the tungsten wire can be refined to the desired wire diameter. Electrolytic polishing can also be performed during the repeated wire drawing process. Electrolytic polishing smooths the surface of the tungsten wire, improves workability, and suppresses wire breakage during drawing.

If the next wire draw is the last one (as in S12), the tungsten wire is annealed (S16). The annealing temperature is between 1200°C and 1600°C. This annealing temperature may be, for example, higher than the temperature of the annealing performed immediately preceding it (S14), but is not limited to this.

Next, the tungsten wire after annealing (S16) is drawn with a low degree of finishing (S18). This low degree of finishing is lower than the finishing in step S10. Specifically, it is between 20% and 50%. For example, drawing with approximately 30% finishing. This final drawing in step S18 creates differential packing within the tungsten wire grains. Furthermore, annealing at temperatures above 1200°C is not performed in steps after S18.

When the final wire drawing finish is greater than 50%, the grain size decreases, making it impossible to reduce the specific resistivity. When the final wire drawing finish is less than 20%, differential packing is not formed within the grains, failing to sufficiently improve the secondary machinability of tungsten wire 1.

Finally, the drawn tungsten wire is subjected to electrolytic polishing (S20). Electrolytic polishing is performed, for example, by immersing the tungsten wire and the counter electrode in an electrolyte such as an aqueous sodium hydroxide solution, thereby creating a potential difference between the tungsten wire and the counter electrode. Through electrolytic polishing, the wire diameter of the tungsten wire is slightly reduced, adjusting it to the desired wire diameter. Alternatively, electrolytic polishing (S20) may not be performed.

The tungsten wire 1 described above can be manufactured through the above steps.

Furthermore, the steps shown in the method for manufacturing tungsten wire 1 are performed, for example, in an inline manner. Specifically, the plurality of wire drawing dies used in step S10 are arranged on the production line in order of decreasing aperture. Additionally, a heating device such as a burner is arranged between each wire drawing die. Furthermore, an electrolytic polishing device may also be arranged between each wire drawing die. Downstream of the wire drawing die used in step S10 (towards subsequent steps), one or more wire drawing dies used in step S18 are arranged in order of decreasing aperture, and an electrolytic polishing device is arranged downstream of the wire drawing die with the smallest aperture. Alternatively, each step may also be performed individually.

[Implementation Examples and Comparative Examples]

Next, specific embodiments and comparative examples of tungsten wire 1 of this embodiment will be explained.

The tungsten wires of Examples 1-3 and Comparative Examples 1-3 have a wire diameter of 24 μm. The tungsten wires of Examples 4-6 and Comparative Examples 4-6 have a wire diameter of 48 μm. Furthermore, the tungsten content of Examples 1-6 and Comparative Examples 1-6 is 99.9 wt% or higher.

The tungsten wire in the embodiments is manufactured according to the manufacturing method shown in Figure 2. The tungsten wire in the comparative examples is drawn with a high degree of finishing instead of the low-finish drawing in step S18 of the manufacturing method shown in Figure 2, or annealed after drawing. The specific manufacturing methods for each embodiment and each comparative example are as follows. Furthermore, the processing methods for embodiments 1-6 and comparative examples 1-6 up to the wire diameter of 180 μm are all the same.

<Implementation Example 1>

In Example 1, tungsten wire with a diameter of 180 μm was annealed at 1500°C (S14), and then drawn with a workability of 80% (S12, drawing before the final drawing) to produce tungsten wire with a diameter of 80 μm. Next, after annealing at 1100°C (S14), it was drawn with a workability of 86% (S12, drawing before the final drawing) to produce tungsten wire with a diameter of 30 μm. Then, after annealing at 1200°C (S16), it was drawn with a workability of 30% (S18) to produce tungsten wire with a diameter of 25.1 μm. Finally, by electrolytic polishing (S20), tungsten wire of Example 1 with a diameter of 24 μm was produced.

<Implementation Example 2>

In Embodiment 2, the manufacturing method is almost identical to that of Embodiment 1, except for the following point: the final annealing before wire drawing in step S16 is performed at 1400°C.

<Implementation Example 3>

In Embodiment 3, the manufacturing method is almost identical to that of Embodiment 1, except for the following point: the final annealing before wire drawing in step S16 is performed at 1600°C.

<Implementation Example 4>

In Example 4, after annealing a tungsten wire with a diameter of 180 μm at 1500°C (S14), it is drawn with a finishing degree of 90% (S12, the first drawing before the final drawing) to produce a tungsten wire with a diameter of 57 μm. Next, after annealing at 1200°C (S16), it is drawn with a finishing degree of 23% (S18) to produce a tungsten wire with a diameter of 50 μm. Then, by performing electrolytic polishing (S20), the tungsten wire of Example 4 with a diameter of 48 μm is produced.

<Implementation Example 5>

In Embodiment 5, the manufacturing method is almost identical to that of Embodiment 4, except for the following point: the final annealing before wire drawing in step S16 is performed at 1400°C.

<Implementation Example 6>

In Embodiment 6, the manufacturing method is almost identical to that of Embodiment 4, except for the following: the final annealing before wire drawing in step S16 is performed at 1600°C.

<Comparative Example 1>

In Comparative Example 1, tungsten wire with a diameter of 180 μm was annealed at 1500°C, and then drawn with a workability of 80% (the first drawing before the final drawing) to produce tungsten wire with a diameter of 80 μm. Next, after annealing at 1100°C, it was drawn with a workability of 91% (the final drawing) to produce tungsten wire with a diameter of 25.1 μm. Subsequently, electrolytic polishing (S20) was performed to produce tungsten wire of Comparative Example 1 with a diameter of 24 μm. Comparative Example 1 represents a case where the workability of the final drawing step (S18) is high, as described in the manufacturing method of this application.

<Comparative example 2>

In Comparative Example 2, the tungsten wire manufactured using the same method as in Comparative Example 1 was annealed at 1400°C after the final wire drawing.

<Comparative Example 3>

In Comparative Example 3, the tungsten wire manufactured using the same method as in Comparative Example 1 was annealed at 1600°C after the final wire drawing.

<Comparative Example 4>

In Comparative Example 4, tungsten wire with a diameter of 180 μm was annealed at 1500°C, and then drawn with a finishing degree of 94% (final drawing) to produce tungsten wire with a diameter of 50 μm. Subsequently, electrolytic polishing (S20) was performed to produce tungsten wire of Comparative Example 4 with a diameter of 48 μm. Comparative Example 4 represents a high finishing degree in the manufacturing method of this application, equivalent to the final drawing step (S18).

<Comparative example 5>

In Comparative Example 5, the tungsten wire manufactured using the same method as in Comparative Example 4 was annealed at 1400°C after the final wire drawing.

<Comparative Example 6>

In Comparative Example 6, the tungsten wire manufactured using the same method as in Comparative Example 4 was annealed at 1600°C after the final wire drawing.

[Evaluation Results]

Next, for the tungsten wires of Examples 1-6 and Comparative Examples 1-6, Tables 1 and 2, and Figures 3A-6B, the results of measuring and evaluating specific resistivity, tensile strength, average crystal width, and secondary processability are explained. For Examples 1-3 and Comparative Examples 2 and 3, the presence or absence of differential packing is also evaluated.

Figures 3A-3F are magnified images showing the surface of the tungsten wires of Examples 1-6, respectively. Figures 4A-4F are magnified images showing the surface of the tungsten wires of Comparative Examples 1-6, respectively. Each figure shows a SEM (Scanning Electron Microscope) image of the surface of the fabricated tungsten wire. In each figure, a range of the same concentration (color) represents one grain. The left-right direction of the paper in each figure is parallel to the axis of the tungsten wire; the surface grains extend in elongated strips along this axis.

In each figure, the solid line L, drawn vertically near the center, is a straight line extending perpendicular to the linear axis. The average width of the surface grains, i.e., the average grain width, is calculated by counting the number of grains and their boundaries (i.e., grain boundaries) along the solid line L within the range shown in each figure. Specifically, the length of the counting range, i.e., the longitudinal length of each figure, is divided by the number of grain boundaries + 1, thus calculating the average width of the surface grains. Additionally, in each figure, multiple short line segments orthogonal to the solid line L represent the locations of the grain boundaries.

Figures 5A-5C are magnified views of the surfaces of the tungsten wires in Examples 1-3 at a higher magnification than Figures 3A-3C. Figures 6A and 6B are magnified views of the surfaces of the tungsten wires in Comparative Examples 2 and 3 at a higher magnification than Figures 4B and 4C.

In Figures 5A-5C, the areas of the differential arrays confirmed within the grains are enclosed in solid lines. In each figure, the subtle irregularities intersecting the tungsten wire axis (left-right direction on the paper) correspond to the differential arrays. Differential arrays are observed in all of Examples 1-3. Furthermore, Examples 4-6, although not shown in the figures, differ only in wire diameter from Examples 1-3 and were manufactured using the same method as Examples 1-3; therefore, it is presumed that they contain differential arrays within the grains.

On the other hand, as shown in Figures 6A and 6B, Comparative Examples 2 and 3, which underwent annealing after the final wire drawing, differ from Figures 5A-5C in that no differential packing was observed. The inventors speculate that this is because the recrystallization of the grains occurs through annealing after wire drawing, thus eliminating the differential packing.

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

[Table 1]

As shown in Table 1, the tungsten wires of Examples 1-3 exhibited lower specific resistance values compared to the tungsten wire of Comparative Example 1. Specifically, the specific resistance improvement rates for Examples 1-3 were 5.6%, 9.6%, and 12.6%, respectively. The specific resistance improvement rate is expressed as a percentage, calculated by subtracting the specific resistance value of each example's tungsten wire from 1 relative to the specific resistance value of the tungsten wire in Comparative Example 1. It was found that a higher final annealing (S16) temperature (e.g., a higher temperature in Comparative Example 3 compared to Comparative Example 1) resulted in lower specific resistance values and a higher improvement rate.

The tungsten wires in Comparative Examples 2 and 3 achieved the same specific resistance as those in Examples 1-3. The inventors speculate that this is due to grain enlargement caused by recrystallization resulting from the annealing performed after the final wire drawing. The average grain width is correlated with both specific resistance and tensile strength. A larger average grain width results in lower specific resistance and lower tensile strength. Conversely, a smaller average grain width results in higher specific resistance and higher tensile strength.

However, in Comparative Examples 2 and 3, although the same specific resistance value as in Examples 1-3 was achieved, the secondary processability was low. The inventors speculate that this is because, as shown in Figures 6A and 6B, differential packing was not present within the grains.

Furthermore, in Tables 1 and 2, "Secondary Processing" indicates whether secondary processing using the tungsten wire in each embodiment or comparative example is possible or impossible. Specifically, as secondary processing, a stranding process using tungsten wire is performed. Stretching is a predetermined stranding process performed on the tungsten wire as the object. Specifically, a bending process is performed with a curvature radius equal to the diameter of the tungsten wire as the object.

In Tables 1 and 2, "Unsuitable" refers to a situation where the tungsten wire breaks during the winding process, making winding impossible. "Suitable" refers to a situation where no tungsten wire breakage occurs, and winding can be performed.

The tungsten wires of Examples 1-3 can all undergo secondary processing. The inventors speculate that this is because, as mentioned above, they contain differential arrangement within the grains. The tungsten wire of Comparative Example 1 can also undergo secondary processing, similar to the examples. However, as mentioned above, the tungsten wire of Comparative Example 1 has a high specific resistance. That is, in Comparative Example 1, both low specific resistance and high secondary processing capability cannot be achieved.

On the other hand, in Comparative Examples 2 and 3, the resistivity was low, but secondary processing was not possible. Specifically, when the aforementioned wire twisting process was performed, the tungsten wire became brittle and broke. That is, in Comparative Examples 2 and 3, both low resistivity and high secondary processing capability could not be achieved.

As mentioned above, tungsten wire with a diameter of 24 μm, in Examples 1-3, achieves both low specific resistance and high reprocessability; in contrast, in Comparative Examples 1-3, it is not possible to achieve both low specific resistance and high reprocessability.

Furthermore, regarding tensile strength, the tungsten wires of Examples 1-3 exhibit lower tensile strength than the tungsten wire of Comparison Example 1. Although the tensile strength is reduced, it is still sufficient to ensure adequate tensile strength for use in fiber products, etc.

Furthermore, as shown in Table 2, the tungsten wires of Examples 4-6, which have a thicker wire diameter than those of Examples 1-3, exhibit the same tendency as in Examples 1-3. Specifically, the tungsten wires of Examples 4-6 have a lower specific resistance value compared to the tungsten wire of Comparative Example 4. More specifically, the specific resistance improvement rates of Examples 4-6 are 5.2%, 10.5%, and 12.6%, respectively.

Regarding the tensile strength, average crystal width, and secondary processability of Examples 4-6, the same tendency as in Examples 1-3 was observed. That is, it was found that, depending on the tungsten wire of each example, both low specific resistivity and high secondary processability can be achieved regardless of the wire diameter.

As described above, in this embodiment of the tungsten wire 1, annealing is performed before the final wire drawing, followed by a final wire drawing with low processing tolerance. This results in tungsten wire 1 with a fine wire diameter, low specific resistivity, and high secondary processing capability.

(Conclusion)

The first-state tungsten wire of this invention, for example, is tungsten wire 1 as described above; its specific resistivity is 6.2 μΩ·cm or more and 6.9 μΩ·cm or less; its wire diameter is 50 μm or less; and it contains differential packing within the grains.

This allows for a balance between low resistance and thin wire diameter. By lowering the specific resistance, it is possible to achieve the same resistance as thicker tungsten wire using thinner tungsten wire (specifically, reducing the cross-sectional area by 5% to 13%). Furthermore, this reduction in cross-sectional area corresponds to the aforementioned improvement in specific resistance.

Furthermore, the first-state tungsten wire exhibits high secondary processing capability due to the inclusion of differential packing within the grains. That is, the first-state tungsten wire can be used for secondary processing of a wide variety of products.

Furthermore, the tungsten wire of the second state of this invention is the same as that of the first state, wherein the tensile strength is 2200 MPa or more and 2800 MPa or less.

This ensures sufficient tensile strength when used in fiber products.

Furthermore, the tungsten line of the third state sample of this invention is the same as that of the first or second state sample, wherein the average width of the surface grains in the direction perpendicular to the linear axis of the tungsten line is 220 nm or more.

This allows for the achievement of low specific resistance.

The fourth state-type fiber product of this invention has tungsten filaments as in any of the first to third state-type products.

This results in a low specific resistance of tungsten wire, making it suitable for use in textile products, particularly in applications utilizing tungsten's conductivity, such as vital sign monitoring. Furthermore, the fine diameter of the tungsten wire is advantageous in textile products that come into direct contact with the skin, such as clothing and towels. For example, a thicker wire diameter results in a poorer feel against the skin; conversely, the fine diameter of the tungsten wire in this embodiment allows for textile products with a pleasant skin feel.

Furthermore, the fifth type of fiber product of this invention is the same as the fourth type of fiber product, wherein the strand 10 is twisted or the mesh 20 is formed.

This allows it to be applied to various types of clothing, etc.

(other)

The tungsten wire and fiber products of the present invention have been described above based on the aforementioned embodiments, but the present invention is not limited to the aforementioned embodiments.

For example, while examples of manufacturing fiber products from tungsten wire through secondary processing are shown, this is not a limited approach. Tungsten wire can also be used, for example, as electrodes in electrochemical processes.

Furthermore, all forms obtainable by performing various modifications within the technical field to which each embodiment pertains, or forms achieved by arbitrarily combining the constituent elements and functions of each embodiment within the scope of the invention's intent, are included in this invention.

1: Tungsten wire

2: Winding spool

10: Twisted yarn (fiber products)

11: Organic Fibers

20: Mesh (fiber products)

Claims (5)

A type of tungsten wire, with a specific resistivity of 6.2 μΩ·cm or higher and 6.9 μΩ·cm or lower; with a wire diameter of 50 μm or less; containing differential packing within its grains. For example, the tungsten wire in Request 1 has a tensile strength of 2200 MPa or higher and 2800 MPa or lower. For example, in the tungsten wire of request item 1 or 2, the average width of the surface grains in the direction perpendicular to the wire axis is 220 nm or more. A fiber product, comprising tungsten yarn as described in any of requests 1 to 3. For example, the fiber products described in request item 4 These fiber products are twisted yarns or mesh sheets.