TUNGSTEN WIRE AND FIBER PRODUCT

Abstract

A tungsten wire has a resistivity of at least 6.2 .Math.cm and at most 6.9 .Math.cm, and a diameter of at most 50 m. Crystal grains of the tungsten wire include dislocation. For example, the tensile strength of the tungsten wire is at least 2200 MPa and at most 2800 MPa.

Claims

1. A tungsten wire, the tungsten wire having: a resistivity of at least 6.2.Math.cm and at most 6.9.Math.cm; and a diameter of at most 50 m, wherein crystal grains of the tungsten wire include dislocation.

2. The tungsten wire according to claim 1, wherein a tensile strength of the tungsten wire is at least 2200 MPa and at most 2800 MPa.

3. The tungsten wire according to claim 1, wherein an average width of surface crystal grains in a direction perpendicular to an axis of the tungsten wire is at least 220 nm.

4. A fiber product comprising: the tungsten wire according to claim 1.

5. The fiber product according to claim 4, wherein the fiber product is a plied yarn or a mesh.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0009] FIG. 1 is a schematic diagram of a tungsten wire and fiber products according to an embodiment.

[0010] FIG. 2 is a flowchart illustrating a method of manufacturing the tungsten wire according to the embodiment.

[0011] FIG. 3A is a diagram illustrating an enlarged view of a surface of a tungsten wire according to Working Example 1.

[0012] FIG. 3B is a diagram illustrating an enlarged view of a surface of a tungsten wire according to Working Example 2.

[0013] FIG. 3C is a diagram illustrating an enlarged view of a surface of a tungsten wire according to Working Example 3.

[0014] FIG. 3D is a diagram illustrating an enlarged view of a surface of a tungsten wire according to Working Example 4.

[0015] FIG. 3E is a diagram Illustrating an enlarged view of a surface of a tungsten wire according to Working Example 5.

[0016] FIG. 3F is a diagram Illustrating an enlarged view of a surface of a tungsten wire according to Working Example 6.

[0017] FIG. 4A is a diagram illustrating an enlarged view of a surface of a tungsten wire according to Comparative Example 1.

[0018] FIG. 4B is a diagram illustrating an enlarged view of a surface of a tungsten wire according to Comparative Example 2.

[0019] FIG. 4C is a diagram illustrating an enlarged view of a surface of a tungsten wire according to Comparative Example 3.

[0020] FIG. 4D is a diagram illustrating an enlarged view of a surface of a tungsten wire according to Comparative Example 4.

[0021] FIG. 4E is a diagram Illustrating an enlarged view of a surface of a tungsten wire according to Comparative Example 5.

[0022] FIG. 4F is a diagram illustrating an enlarged view of a surface of a tungsten wire according to Comparative Example 6.

[0023] FIG. 5A is a diagram illustrating, under higher magnification than in FIG. 3A, an enlarged view of the surface of the tungsten wire according to Working Example 1.

[0024] FIG. 5B is a diagram illustrating, under higher magnification than in FIG. 3B, an enlarged view of the surface of the tungsten wire according to Working Example 2.

[0025] FIG. 5C is a diagram illustrating, under higher magnification than in FIG. 3C, an enlarged view of the surface of the tungsten wire according to Working Example 3.

[0026] FIG. 6A is a diagram illustrating, under higher magnification than in FIG. 4B, an enlarged view of the surface of the tungsten wire according to Comparative Example 2.

[0027] FIG. 6B is a diagram illustrating, under higher magnification than in FIG. 4C, an enlarged view of the surface of the tungsten wire according to Comparative Example 3.

DESCRIPTION OF EMBODIMENTS

[0028] Hereinafter, a tungsten wire and a fiber product according to embodiments of the present invention will be described in detail with reference to the Drawings. It should be noted that each of the embodiments described shows a specific example of the present Invention. Therefore, numerical values, shapes, materials, elements, the arrangement and connection of the elements, steps, the processing order of the steps, etc., indicated in the following embodiments are mere examples, and thus are not intended to limit the present invention. Accordingly, among the elements described in the following embodiments, elements not recited in any independent claim are described as optional elements.

[0029] Furthermore, the figures are schematic illustrations and are not necessarily accurate depictions. Therefore, for example, the scaling, etc., in the figures is not necessarily uniform. Elements which are substantially the same have the same reference signs in the figures, and duplicate description may be omitted or simplified.

[0030] In the Written Description, terms indicating relationships between elements, terms indicating shapes of elements, and numerical ranges are expressions that refer not only to their strict meanings, but encompass a range of essentially equivalents, such as a range of deviations of a few percent.

EMBODIMENT

Configuration

[0031] First, the configuration of a tungsten wire and a fiber product according to the present embodiment will be described with reference to FIG. 1. FIG. 1 is a schematic diagram illustrating tungsten wire 1 and fiber products according to the present embodiment.

[0032] As illustrated in FIG. 1, tungsten wire 1 is wound around winding frame 2 and stored. Winding frame 2 may be referred to as a bobbin, reel, spool, drum, or the like in some instances. Tungsten wire 1 has, for example, but not particularly limited to, a total length ranging from the order of meters, such as approximately 100 m, to the order of kilometers.

[0033] Tungsten wire 1 illustrated in FIG. 1 can be subjected to secondary working. That is, tungsten wire 1 is worked to form a part of a product. The product is, for example, a fiber product that includes at least one tungsten wire 1 having a predetermined length. The fiber product is a conductive fiber with conductivity of tungsten wire 1.

[0034] Plied yarn 10 is illustrated in FIG. 1 as an example of a fiber product. Plied yarn 10 includes tungsten wire 1 and organic fiber 11 that is combined with tungsten wire 10.

[0035] Plied yarn 10 is a covered yarn in which organic fiber 10 is a core yarn and tungsten wire 10 is a sheath yarn. Plied yarn 10 is manufactured by, for example, extending and fixing organic fiber 11 as the core yarn and winding tungsten wire 1 around organic fiber 11 as the sheath yarn (that is, performing a covering process).

[0036] Tungsten wire 1 is wound along an outer surface of organic fiber 11 with a predetermined pitch. As illustrated in FIG. 1, tungsten wire 1 is wound with a gap between adjacent turns. However, the adjacent turns may be in close contact with each other. A specific configuration and a specific manufacturing method of tungsten wire 10 will be described later.

[0037] Organic fiber 11 is at least one fiber selected from a group containing a synthetic fiber, a natural fiber, and a recycled fiber. Organic fiber 11 is, for example, a synthetic fiber such as an aramid fiber, a nylon-based fiber, or a polyethylene-based fiber. As the aramid fiber, for example, a fiber manufactured using an aromatic polyamide-based resin material such as Kevlar (registered trademark) can be used. As the polyethylene-based fiber, for example, a fiber manufactured using an ultra-high-molecular-weight polyethylene such as Dyneema (registered trademark) can be used.

[0038] It should be noted that a chemical fiber used as organic fiber 11 is not limited to these, and other chemical fibers such as polyester, polypropylene, polyurethane, polyvinyl chloride, or acrylic can be used. Alternatively, organic fiber 11 may be a semi-synthetic fiber or a recycled fiber. Furthermore, organic fiber 11 may be a natural fiber such as a plant fiber or an animal fiber. For example, as organic fiber 11, cotton, wool, silk, hemp, rayon, or the like can be used.

[0039] It should be noted that plied yarn 10 may be a covered yarn that includes tungsten wire 1 as a core yarn and organic fiber 11 as a sheath yarn. Alternatively, plied yarn 10 is not limited to a covered yarn and may be a doubled-and-twisted yarn.

[0040] Alternatively, plied yarn 10 may include a plurality of tungsten wires 1 rather than organic fiber 11. Plied yarn 10 may be manufactured by performing twisting processing (e.g., covering processing or doubling-and-twisting processing) on a plurality of tungsten wires 1. Alternatively, plied yarn 10 may be a plied yarn of tungsten wire 1 and another type of metal wire such as a stainless wire.

[0041] FIG. 1 also illustrates mesh 20 as an example of another fiber product. Mesh 20 includes a plurality of tungsten wires 1. Mesh 20 is manufactured by performing weaving processing using the plurality of tungsten wires 1 as warp yarns and weft yarns. A weave pattern of mesh 20 is plain weave, twill weave, Dutch weave, satin weave, or the like. The weave pattern is not limited to a particular weave pattern. Mesh 20 may be manufactured by performing knitting processing such as stockinette stitch with a predetermined gauge using the plurality of tungsten wires 1 as knitting yarns.

[0042] It should be noted that mesh 20 may be manufactured by performing weaving processing or knitting processing using plied yarn 10. Alternatively, mesh 20 may be formed in a three-dimensional shape. For example, mesh 20 may form gloves, a hat, or clothes.

[0043] The fiber product such as plied yarn 10 or mesh 20 includes tungsten wire 1 having conductivity and thus can be used in, for example, vital sensing. For example, the fiber product can sense, as an example of a vital sign, a body temperature or a pulse of a wearer. Specifically, tungsten wire 1 included in the fiber product functions as terminals for sensing the vital sign. That is, tungsten wire 1 can detect a weak current generated by the wearer.

[0044] Alternatively, the fiber product may separately include terminals for sensing a vital sign. In this case, tungsten wire 1 functions as wiring that electrically connects the terminals and a signal processing circuit.

[0045] Alternatively, the fiber product may be used for generating heat. Specifically, heat can be generated by causing current to flow through tungsten wire 1 included in the fiber product.

[0046] The fiber product may be clothing including gloves, clothes, headgear such as a hat, footgear such as socks or Japanese socks, or the like. Alternatively, the fiber product may be a towel, a hand towel, a handkerchief, a blanket, a sheet, or the like.

[0047] Alternatively, the fiber product may be a non-woven fabric manufactured by performing non-woven processing using tungsten wire 1 and organic fiber 11 as thread materials. Alternatively, the fiber product may be tungsten wires 1 or plied yarns 10 collected in a form of a cotton pellet. Alternatively, the fiber product may be a woven fabric manufactured using an organic fiber or may be a fiber fabric such as a knitted fabric or a braided fabric into which tungsten wire 1 is sewn (embroidery or sewing) afterward.

[Tungsten Wire]

[0048] Subsequently, a specific configuration of tungsten wire 1 according to the present embodiment will be described.

[0049] Tungsten wire 1 is a metal wire that contains tungsten (W) as a major component. The term major component means that the content of a target element (here, tungsten) is greater than 50 wt %. For example, the content of tungsten contained in tungsten wire 1 is at least 90 wt %. The content of tungsten may be at least 95 wt %, at least 99 wt %, or at least 99.9 wt %. It should be noted that the content of tungsten is a proportion of a weight of tungsten with respect to a weight of tungsten wire 1. Tungsten wire 1 may be a pure tungsten wire that is substantially 100 wt % in its content. It should be noted that the pure tungsten wire may contain inevitable impurities, which are inevitably mixed therein in the manufacture.

[0050] Tungsten wire 1 may be a tungsten alloy wire formed from an alloy of tungsten and a metallic element other than tungsten. The metallic element other than tungsten is, for example, rhenium (Re), ruthenium (Ru), iridium (Ir), osmium (Os), or the like. A content of the metallic element, such as rhenium, included in the alloy (solid solution) is, for example, but not limited to, at least 0.1 wt % and at most 10 wt %. The content of the metallic element included in the alloy may be at least 0.5 wt % and at most 5 wt %. As an example, a content of rhenium is 1 wt % but may be 3 wt %.

[0051] Alternatively, tungsten wire 1 may be a doped tungsten wire that is doped with a predetermined element (doped element) such as potassium (K) or cerium (Ce). A content of the doped element is, for example, but not limited to, at least 0.005 wt % and at most 0.010 wt %.

[0052] Tungsten wire 1 has a diameter that is at most 50 m. For example, the diameter of tungsten wire 1 may be at most 40 m, at most 30 m, at most 20 m, or at most 10 m. For example, the diameter of tungsten wire 1 may be approximately 5 m.

[0053] Tungsten wire 1 has a tensile strength that is at least 2200 MPa and at most 2800 MPa. Accordingly, it is possible to ensure sufficient tensile strength for use as a fiber product, or the like.

[0054] An average width of surface crystal grains in a direction perpendicular to an axis of tungsten wire 1 is at least 220 nm. The average width of the surface crystal grains (hereinafter, referred to as an average crystal width) is one of parameters that Indicate sizes of crystal grains included in tungsten wire 1. A specific method of measuring the average crystal width will be described with working examples. The average crystal width is, for example, at least 220 nm and at most 310 nm.

[0055] The average crystal width being at least 220 nm reduces a resistivity of tungsten wire 1. That is, when the size of the crystal grains of tungsten wire 1 increases, grain boundaries in tungsten wire 1 are reduced. When current flows through tungsten wire 1, the grain boundaries interfere with movement of electrons, thus producing an electric resistance. In the present embodiment, it is possible to reduce the resistivity of tungsten wire 1 by reducing the grain boundaries. Specifically, the resistivity of tungsten wire 1 is at least 6.2 .Math.cm and at most 6.9 .Math.cm.

[0056] The crystal grains of tungsten wire 1 include dislocations. The dislocations are linear crystallographic defects. The dislocations occur in a drawing process (wire drawing process) in the method of manufacturing tungsten wire 1, The occurring dislocations substantially disappear (to an extent that the dislocations cannot be observed at a predetermined magnification) when tungsten wire 1 is subjected to heating (annealing) at a predetermined temperature (e.g., 1200 C.) or higher. In other words, tungsten wire 1 including such dislocations that can be observed at the predetermined magnification means that tungsten wire 1 is not subjected to the above-described heating at the predetermined temperature described above or higher after a final drawing process.

[0057] Furthermore, dislocations included in the crystal grains of tungsten wire 1 increase a secondary workability of tungsten wire 1. For example, when tungsten wires 1 having the same diameter are compared, tungsten wire 1 including dislocations has a secondary workability higher than a secondary workability of a tungsten wire including no dislocations. Specifically, tungsten wire 1 including dislocations increases in flexibility (bendability) to be capable of being subjected to secondary working involving folding or bending such as twisting processing, weaving processing, or net making processing using tungsten wire 1. This is because propagation of force applied to tungsten wire 1 in the secondary working is suppressed by dislocations in crystal grains, and thus occurrence of wire breakage or the like of tungsten wire 1 can be suppressed.

[0058] It should be noted that dislocations do not occur only by occurrence of elastic deformation. For example, dislocations do not occur only by winding tungsten wire 1 around winding frame 2 to be stored as illustrated in FIG. 1.

[0059] As described above, tungsten wire 1 according to the present embodiment can achieve both low resistance and narrow diameter. In addition, tungsten wire 1 according to the present embodiment can be subjected to the secondary working such as twisting processing, thus enabling manufacture of the above-described fiber products.

[Manufacturing Method]

[0060] Next, a method of manufacturing tungsten wire 1 according to the present embodiment will be described with reference to FIG. 2. FIG. 2 is a flowchart illustrating a method of manufacturing tungsten wire 1 according to the present embodiment.

[0061] First, as illustrated in FIG. 2, drawing at a high working ratio is performed on a tungsten wire having a predetermined diameter (e.g., approximately 3 mm) that is thicker than a diameter set as a final diameter (S10). The tungsten wire having the predetermined diameter is produced by repeatedly performing swaging processing, rolling processing, or the like on a tungsten ingot. Furthermore, the tungsten ingot is produced by performing pressing and sintering on a prepared aggregate of tungsten powder. It should be noted that, by mixing powder of the alloying element or powder of the doped element into the tungsten powder, it is possible to manufacture the tungsten alloy wire or the doped tungsten wire.

[0062] The working ratio is the percentage reduction in cross-sectional area due to the drawing. Specifically, the working ratio is a value obtained by subtracting a ratio of a cross-sectional area of the tungsten wire after the drawing with respect to the cross-sectional area of the tungsten wire before the drawing from one and is expressed in terms of a percentage. The higher the working ratio, the more an amount of reduction in the cross-sectional area by the drawing, and the lower the working ratio, the less the amount of reduction in the cross-sectional area by the drawing. That is, when tungsten wires having the same diameter are subjected to the drawing, a diameter of a tungsten wire subjected to the drawing at a high working ratio is narrower than a diameter of a tungsten wire subjected to the drawing at a low working ratio.

[0063] In Step S10, the high working ratio is specifically a working ratio of at least 80%. For example, the drawing is executed at a working ratio of at least 80% and at most 95%.

[0064] The drawing is performed using one or more wire drawing dies. In the drawing process, a lubricant made of graphite dispersed in water may be used. It should be noted that annealing may be performed on the tungsten wire before first drawing. By performing the annealing, an oxide layer is formed on a surface of the tungsten wire. Accordingly, occurrence of wire breakage during drawing processing can be suppressed.

[0065] When next drawing is not final (No in S12), annealing is performed on the tungsten wire (S14). By performing the annealing, it is possible to suppress deterioration in workability in the drawing. A temperature of the annealing is, for example, but not limited to, a temperature at least 1000 C. and at most 1600 C. After performing the annealing, the method returns to Step S10, where the drawing is performed at the high working ratio. By repeating the drawing (S10) and the annealing (S14), reduction of the diameter is performed until the tungsten wire has a desired diameter. In the repetition of the drawing, electrolytic polishing may be performed in a midcourse. By the electrolytic polishing, the surface of the tungsten wire can be smoothed, and thus the workability can be increased to suppress the occurrence of wire breakage during the drawing.

[0066] When next drawing is final (Yes in S12), annealing is performed on the tungsten wire (S16). A temperature of the annealing is a temperature at least 1200 C. and at most 1600 C. This temperature of the annealing is, for example, but not limited to, a temperature higher than the temperature of the immediately previous annealing (S14).

[0067] Next, the tungsten wire after the annealing (S16) is subjected to the drawing at a low working ratio (S18). The low working ratio here is a working ratio lower than the working ratio in Step S10. Specifically, the low working ratio is at least 20% and at most 50%. For example, the drawing is executed at a working ratio of approximately 30%. By the final drawing in Step S18, dislocations are formed in crystal grains of the tungsten wire. It should be noted that, in a process after Step S18, annealing at a temperature of at least 1200 C. is not performed.

[0068] If the working ratio in the final drawing is greater than 50%, the crystal grains become small, failing to reduce the resistivity. If the working ratio in the final drawing is less than 20%, dislocations are not formed in the crystal grains, failing to increase the secondary workability of tungsten wire 1 sufficiently.

[0069] Finally, the tungsten wire after the drawing is subjected to electrolytic polishing (S20). The electrolytic polishing is carried out, for example, as a result of generation of a potential difference between the tungsten wire and a counter electrode in a state in which the tungsten wire and the counter electrode are bathed into electrolyte such as aqueous sodium hydroxide. By the electrolytic polishing, the diameter of the tungsten wire is slightly reduced to be adjusted to the desired diameter. It should be noted that the electrolytic polishing (S20) need not be performed.

[0070] Through the above-described processes, above-described tungsten wire 1 can be manufactured.

[0071] Each of the processes indicated in the manufacturing method of tungsten wire 1 is carried out, for example, as an in-line process. More specifically, the plurality of wire drawing dies used in Step S10 are arranged in descending order of pore diameters in a production line. Furthermore, a heating device such as a burner is disposed between the respective wire drawing dies. In addition, an electrolytic polishing device may be disposed between the respective wire drawing dies. The one or more wire drawing dies used in Step S18 are arranged in descending order of pore diameters on the downstream side (i.e., the subsequent-process side) of the wire drawing dies used in Step S10, and the electrolytic polishing device is disposed on the downstream side of the wire drawing die having the smallest pore diameter. It should be noted that each of the processes may be individually performed.

WORKING EXAMPLES AND COMPARATIVE EXAMPLES

[0072] Next, specific working examples of tungsten wire 1 according to the present embodiment and comparative examples will be described.

[0073] Tungsten wires according to Working Examples 1 to 3 and Comparative Examples 1 to 3 are tungsten wires having a diameter of 24 m. Tungsten wires according to Working Examples 4 to 6 and Comparative Examples 4 to 6 are tungsten wires having a diameter of 48 m. It should be noted that tungsten content of the tungsten wires according to Working Examples 1 to 6 and Comparative Examples 1 to 6 are at least 99.9 wt %.

[0074] The tungsten wires according to the working examples were manufactured according to the manufacturing method illustrated in FIG. 2. The tungsten wires according to the comparative examples were subjected to the drawing at the high working ratio or subjected to the drawing at the high working ratio and then the annealing, instead of the drawing at the low working ratio in Step S18 in the manufacturing method illustrated in FIG. 2. Specific manufacturing methods in the working examples and the comparative examples are as follows. It should be noted that, in all of Working Examples 1 to 6 and Comparative Examples 1 to 6, processing methods for bringing their diameters to 180 m are the same.

Working Example 1

[0075] In Working Example 1, its tungsten wire having a diameter of 180 m was subjected to the annealing (S14) at 1500 C. and then subjected to the drawing at a working ratio of 80% (S12, the drawing two drawings before the final drawing) to be formed into a tungsten wire having a diameter of 80 m. Next, the tungsten wire was subjected to the annealing (S14) at 1100 C. and then subjected to the drawing at a working ratio of 86% (S12, the drawing one drawing before the final drawing) to be formed into a tungsten wire having a diameter of 30 m. Next, the tungsten wire was subjected to the annealing (S16) at 1200 C. and then subjected to the drawing (S18) at a working ratio of 30% to be formed into a tungsten wire having a diameter of 25.1 m. Then, the tungsten wire was subjected to the electrolytic polishing (S20) to be formed into a tungsten wire according to Working Example 1 having a diameter of 24 m.

Working Example 2

[0076] Working Example 2 is substantially the same as Working Example 1 in the manufacturing method and differs from Working Example 1 only in that the annealing in Step S16 previous to the final drawing was performed at 1400 C.

Working Example 3

[0077] Working Example 3 is substantially the same as Working Example 1 in the manufacturing method and differs from Working Example 1 only in that the annealing in Step S16 previous to the final drawing was performed at 1600 C.

Working Example 4

[0078] In Working Example 4, its tungsten wire having a diameter of 180 m was subjected to the annealing (S14) at 1500 C. and then subjected to the drawing at a working ratio of 90% (S12, the drawing one drawing before the final drawing) to be formed into a tungsten wire having a diameter of 57 m. Next, the tungsten wire was subjected to the annealing (S16) at 1200 C. and then subjected to the drawing (S18) at a working ratio of 23% to be formed into a tungsten wire having a diameter of 50 m. Then, the tungsten wire was subjected to the electrolytic polishing (S20) to be formed into a tungsten wire according to Working Example 4 having a diameter of 48 m.

Working Example 5

[0079] Working Example 5 is substantially the same as Working Example 4 in the manufacturing method and differs from Working Example 4 only in that the annealing in Step S16 previous to the final drawing was performed at 1400 C.

Working Example 6

[0080] Working Example 6 is substantially the same as Working Example 4 in the manufacturing method and differs from Working Example 4 only in that the annealing in Step S16 previous to the final drawing was performed at 1600 C.

Comparative Example 1

[0081] In Comparative Example 1, its tungsten wire having a diameter of 180 m was subjected to annealing at 1500 C. and then subjected to drawing at a working ratio of 80% (the drawing one drawing before final drawing) to be formed into a tungsten wire having a diameter of 80 m. Next, the tungsten wire was subjected to annealing at 1100 C. and then subjected to drawing (final drawing) at a working ratio of 91% to be formed into a tungsten wire having a diameter of 25.1 m. Then, the tungsten wire was subjected to the electrolytic polishing (S20) to be formed into a tungsten wire according to Comparative Example 1 having a diameter of 24 m. Comparative Example 1 corresponds to a case where the working ratio in the final drawing process (S18) is high in the manufacturing method according to the present application.

Comparative Example 2

[0082] In Comparative Example 2, a tungsten wire manufactured by the same manufacturing method as in Comparative Example 1 was subjected to annealing at 1400 C. after the final drawing.

Comparative Example 3

[0083] In Comparative Example 3, a tungsten wire manufactured by the same manufacturing method as in Comparative Example 1 was subjected to annealing at 1600 C. after the final drawing.

Comparative Example 4

[0084] In Comparative Example 4, Its tungsten wire having a diameter of 180 m was subjected to annealing at 1500 C. and then subjected to drawing at a working ratio of 94% (final drawing) to be formed into a tungsten wire having a diameter of 50 m. Then, the tungsten wire was subjected to the electrolytic polishing (S20) to be formed into a tungsten wire according to Comparative Example 4 having a diameter of 48 m. Comparative Example 4 corresponds to a case where the working ratio in the final drawing process (S18) is high in the manufacturing method according to the present application.

Comparative Example 5

[0085] In Comparative Example 5, a tungsten wire manufactured by the same manufacturing method as in Comparative Example 4 was subjected to annealing at 1400 C. after the final drawing.

Comparative Example 6

[0086] In Comparative Example 6, a tungsten wire manufactured by the same manufacturing method as in Comparative Example 4 was subjected to annealing at 1600 C. after the final drawing.

Evaluation Result

[0087] Subsequently, the above-described tungsten wires according to Working Examples 1 to 6 and Comparative Examples 1 to 6 were subjected to measurement and evaluation about the resistivity, the tensile strength, the average crystal width, and the secondary workability, and result of the measurement and evaluation will be described with reference to Table 1 and Table 2, and FIG. 3A to FIG. 6B. For Working Examples 1 to 3, and Comparative Examples 2 and 3, presence or absence of dislocations was also evaluated.

[0088] FIG. 3A to FIG. 3F are diagrams illustrating enlarged views of surfaces of the tungsten wires according to Working Examples 1 to 6, respectively. FIG. 4A to FIG. 4F are diagrams Illustrating enlarged views of surfaces of the tungsten wires according to Comparative Examples 1 to 6, respectively. The figures illustrate scanning electron microscope (SEM) images of the surfaces of the formed tungsten wire. In the figures, a region of the same depth (color) depicts one crystal grain. In each of the figures, a right-left direction of the paper is a direction parallel to an axis of a corresponding tungsten wire, and surface crystal grains extend long in a direction along the axis.

[0089] In the figures, solid line L drawn vertically at a vicinity of the center is a straight line extending in a direction perpendicular to the axis. The average width of the surface crystal grains, that is, the average crystal width is calculated by counting the number of boundaries between crystal grains (i.e., grain boundaries) along solid line L within a region Illustrated in each of the figures. Specifically, the average width of the surface crystal grains is calculated by dividing a length of the region for the counting, that is, a vertical length of each of the figures by the grain boundary count+1. It should be noted that, in each of the figures, a plurality of short segments orthogonal to solid line L each indicate positions of the grain boundaries.

[0090] FIG. 5A to FIG. 5C are diagrams illustrating, under higher magnification than in FIG. 3A to FIG. 3C, enlarged views of the surfaces of the tungsten wires according to Working Examples 1 to 3, respectively. FIG. 6A and FIG. 6B are diagrams illustrating, under higher magnification than in FIG. 4B and FIG. 4C, enlarged views of the surfaces of the tungsten wires according to Comparative Examples 2 and 3, respectively.

[0091] In FIG. 5A to FIG. 5C, regions where dislocations included in crystal grains are observed are enclosed with solid frames, respectively. In each of the figures, projections and depressions that finely appear intersecting in an axial direction of a corresponding tungsten wire (a right-left direction of the paper in the figures) correspond to dislocations. It is understood that dislocations appear in all of Working Examples 1 to 3. It should be noted that, in Working Examples 4 to 6, which differ from Working Examples 1 to 3 only in diameter, it can be assumed that dislocations are also included in their crystal grains, which are not illustrated in the figures, because the tungsten wires according to Working Examples 4 to 6 are manufacture by the same manufacturing method as in Working Examples 1 to 3.

[0092] In contrast, as Illustrated in FIG. 6A and FIG. 6B, dislocations were not observed in Comparative Examples 2 and 3, in which the annealing was performed after the final drawing, unlike FIG. 5A to FIG. 5C. It can be assumed that the annealing after the drawing advances recrystallization of the crystal grains, thus causing the dislocations to disappear.

[0093] Table 1 shows results of the evaluation of the tungsten wires according to Working Examples 1 to 3 and Comparative Examples 1 to 3 (diameter: 24 m). Table 2 shows results of the evaluation of the tungsten wires according to Working Examples 4 to 6 and Comparative Examples 4 to 6 (diameter: 48 m).

TABLE-US-00001 TABLE 1 Tensile Average Resistivity strength crystal width Secondary Diameter: 24 m [ .Math. cm] [MPa] [nm] working Dislocation Working example 1 6.81 2720 224 Yes Yes Working example 2 6.53 2480 231 Yes Yes Working example 3 6.31 2310 277 Yes Yes Comparative example 1 7.22 3250 202 Yes Comparative example 2 6.64 2650 218 No No Comparative example 3 6.30 2470 296 No No

TABLE-US-00002 TABLE 2 Average Tensile crystal Resistivity strength width Secondary Diameter: 48 m [ .Math. cm] [MPa] [nm] working Working example 4 6.77 2680 224 Yes Working example 5 6.39 2420 244 Yes Working example 6 6.24 2270 307 Yes Comparative example 4 7.14 3110 207 Yes Comparative example 5 6.54 2580 224 No Comparative example 6 6.27 2350 346 No

[0094] As shown in Table 1, the tungsten wires according to Working Examples 1 to 3 have resistivities lower than a resistivity of the tungsten wire according to Comparative Example 1. Specifically, resistivity improvement rates of Working Examples 1 to 3 were 5.6%, 9.6%, and 12.6%. It should be noted that the resistivity improvement rate is a value obtained by subtracting a ratio of a resistivity of the tungsten wire according to each of the working examples with respect to a resistivity of the tungsten wire according to Comparative Example 1 from one and is expressed in terms of a percentage. It is understood that a higher temperature of the final annealing (S16) (e.g., Comparative Example 3 compared with Comparative Example 1) results in a lower resistivity and a higher improvement rate.

[0095] The tungsten wires according to Comparative Examples 2 and 3 realize resistivities on a par with the resistivities of the tungsten wires according to Working Examples 1 to 3. It can be assumed that this is due to coarsening of crystal grains through recrystallization by the annealing performed after the final drawing. The average crystal width has a correlation with the resistivity and the tensile strength. The larger the average crystal width, the lower the resistivity, and the lower the tensile strength. The smaller the average crystal width, the higher the resistivity, and the higher the tensile strength.

[0096] However, while realizing the resistivities on a par with the resistivities of the tungsten wires according to Working Examples 1 to 3, the tungsten wires according to Comparative Examples 2 and 3 are low in the secondary workability. It can be assumed that this is due to their crystal grains including no dislocations, as illustrated in FIG. 6A and FIG. 6B.

[0097] It should be noted that, in Table 1 and Table 2, secondary working indicates whether the secondary working using the tungsten wire according to each of the working examples or the comparative examples was feasible or not. Specifically, as the secondary working, the twisting processing using the tungsten wire was performed. The twisting processing is predetermined twisting processing performed on a target tungsten wire. Specifically, the target tungsten wire was subjected to work in which the target tungsten wire was bent with a radius of curvature that was equal to the diameter of the target tungsten wire.

[0098] No in Table 1 and Table 2 means that wire breakage of the tungsten wire occurred in the middle of the twisting processing, and the twisting processing failed. Yes means that the twisting processing was successfully performed without the occurrence of the wire breakage of the tungsten wire.

[0099] All of the tungsten wires according to Working Examples 1 to 3 were capable of being subjected to the secondary working. It can be assumed that this is due to their crystal grains including dislocations as described above. The tungsten wire according to Comparative Example 1 was also capable of being subjected to the secondary working as in the working examples. However, the tungsten wire according to Comparative Example 1 is high in resistivity as described above. That is, Comparative Example 1 failed to realize low resistivity and high secondary workability.

[0100] In contrast, the tungsten wires according to Comparative Examples 2 and 3 were low in resistivity but failed to be subjected to the secondary working. Specifically, their tungsten wires were so brittle that wire breakage occurred when the above-described twisting processing was performed. That is, Comparative Examples 2 and 3 also failed to realize low resistivity and high secondary workability.

[0101] As described above, it is understood that, in a case of tungsten wires having a diameter of 24 m, Working Examples 1 to 3 successfully achieved low resistivity and high secondary workability, while Comparative Examples 1 to 3 failed to achieve low resistivity and high secondary workability.

[0102] It should be noted that the tungsten wires according to Working Examples 1 to 3 were lower in tensile strength then the tungsten wires according to Comparative Example 1. Although the tensile strengths are decreased, it is possible to ensure sufficient tensile strengths for use as the fiber product or the like.

[0103] In addition, as shown in Table 2, the tungsten wires according to Working Examples 4 to 6, which are thicker than the tungsten wires according to Working Examples 1 to 3 in diameter, shows the same tendency as in Working Examples 1 to 3. Specifically, the tungsten wires according to Working Examples 4 to 6 have resistivities lower than a resistivity of the tungsten wire according to Comparative Example 4. More specifically, resistivity improvement rates of Working Examples 4 to 6 were 5.2%, 10.5%, and 12.6%,

[0104] Tensile strengths, average crystal widths, and secondary workabilities of the tungsten wires according to Working Examples 4 to 6 showed the same tendencies as in Working Examples 1 to 3. That is, it is understood that the tungsten wires according to the working examples each successfully achieved both low resistivity and high secondary workability irrespective of a size of the diameter.

[0105] As described above, tungsten wire 1 according to the present embodiment is subjected to the annealing before the final drawing and then to the final drawing at the low working ratio. Accordingly, it is possible to provide tungsten wire 1 that realizes narrow diameter, low resistivity, and high secondary workability.

CONCLUSION

[0106] A tungsten wire according to a first aspect of the present Invention is, for example, above-described tungsten wire 1 and has: a resistivity of at least 6.2 .Math.cm and at most 6.9 .Math.cm; and a diameter of at most 50 m, in which crystal grains of the tungsten wire include dislocation.

[0107] Accordingly, it is possible to achieve both low resistance and narrow diameter. With the low resistivity, it is possible to realize an electric resistance on a par with an electric resistance of a thick tungsten wire with narrow tungsten wire 1 (specifically, with a reduction in cross-sectional area of 5% to 13%). It should be noted that a proportion of this reduction in cross-sectional area corresponds to the above-described resistivity improvement rate.

[0108] In addition, the tungsten wire according to the first aspect can realize high secondary workability by including dislocations in its crystal grains. That is, the tungsten wire according to the first aspect can be used in the secondary working for various products.

[0109] Furthermore, a tungsten wire according to a second aspect of the present invention is the tungsten wire according to the first aspect, in which a tensile strength of the tungsten wire is at least 2200 MPa and at most 2800 MPa.

[0110] Accordingly, it is possible to ensure sufficient tensile strength for use as a fiber product, or the like.

[0111] Furthermore, a tungsten wire according to a third aspect of the present invention is the tungsten wire according to the first or the second aspect, in which an average width of surface crystal grains in a direction perpendicular to an axis of the tungsten wire is at least 220 nm.

[0112] Accordingly, low resistivity can be realized.

[0113] A fiber product according to a fourth aspect of the present invention includes the tungsten wire according to any one of the first to third aspects.

[0114] Accordingly, since the tungsten wire has low resistivity, the fiber product can be used in, for example, vital sensing using conductivity of the tungsten wire. In addition, the narrow diameter of the tungsten wire is useful in a fiber product that is directly used by a person, such as clothing and a towel. For example, while a thick diameter results in an unpleasant texture, the narrow diameter of the tungsten wire according to the present embodiment can realize a fiber product with a good texture.

[0115] Furthermore the fiber product according to a fifth aspect of the present invention is the fiber product according to the fourth aspect, in which the fiber product is a plied yarn or a mesh.

[0116] Accordingly, application to a large variety of clothing is possible.

OTHERS

[0117] Although the tungsten wire and the fiber product according to the present invention have been described based on the foregoing embodiment, and so on, the present invention is not limited to the foregoing embodiment.

[0118] For example, the example in which the secondary working is performed on the tungsten wire to manufacture the fiber product is described, but the present invention is not limited to this. The tungsten wire may be used as, for example, electrodes for electric discharge machining.

[0119] Aside from the above, forms obtained by various modifications to respective embodiments that can be conceived by those skilled in the art, as well as forms realized by combining constituent elements in the respective embodiments, without materially departing from the spirit of the present disclosure are included in the present invention.

REFERENCE SIGNS LIST

[0120] 1 tungsten wire [0121] 10 plied yarn (fiber product) [0122] 20 mesh (fiber product)