Metal wire and metal mesh

Abstract

The metal wire (10) is made of tungsten or tungsten alloy, has a wire diameter of 13 μm or less, a tensile strength of 4.8 GPa or more, and a natural vertical drop length of 800 mm or more per 1000 mm.

Description

Metal wire and metal mesh Technical Field

[0001] This invention relates to metal wires and metal meshes. Background Technology

[0002] Previously, tungsten wires with small diameter and high tensile strength were known (see, for example, Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2020-105548 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] However, with respect to the aforementioned conventional tungsten wires, when the wire diameter is reduced while maintaining high tensile strength, there is a problem of decreased straightness (linearity).

[0008] Therefore, the object of the present invention is to provide a metal wire with small diameter and excellent tensile strength and straightness, and a metal mesh having the metal wire.

[0009] Methods for solving problems

[0010] In one embodiment of the present invention, the metal wire is made of tungsten or a tungsten alloy, the wire diameter is less than 13 μm, the tensile strength is greater than 4.8 GPa, and the natural droop length per 1000 mm is greater than 800 mm.

[0011] One embodiment of the present invention has a metal mesh comprising the metal wires described above as warp or weft yarns.

[0012] Invention Effects

[0013] According to the present invention, it is possible to provide metal wires with small diameter and excellent tensile strength and straightness. Attached Figure Description

[0014] Figure 1 is a schematic diagram of a metal mesh with metal wires according to an embodiment.

[0015] Figure 2A is a flowchart illustrating a method for manufacturing a metal wire according to an embodiment.

[0016] Figure 2B is a flowchart illustrating another example of a method for manufacturing a metal wire according to an embodiment.

[0017] Figure 3 is a graph showing the relationship between the straightness and tensile strength of the metal wire in the embodiment.

[0018] Figure 4 is a graph showing the relationship between the wire diameter non-uniformity and tensile strength of the metal wire in the embodiment. Detailed Implementation

[0019] The metal wire and metal mesh according to embodiments of the present invention will now be described in detail using the accompanying drawings. It should be noted that the embodiments described below are specific examples of the present invention. Therefore, the values, shapes, materials, constituent elements, arrangements and connection methods of constituent elements, steps, and order of steps shown in the following embodiments are merely examples and do not limit the scope of the present invention. Therefore, constituent elements not described in the independent claims among the constituent elements in the following embodiments are described as optional constituent elements.

[0020] Furthermore, these figures are schematic diagrams and may not be perfectly accurate. Therefore, for example, the scales may not be consistent across different figures. Additionally, in each figure, substantially identical components are labeled with the same symbol, and repetitive descriptions are omitted or simplified.

[0021] Furthermore, in this specification, terms and numerical ranges used to describe the shape of elements, such as circles, are not merely expressions with a strict meaning, but rather imply expressions that also include substantially equivalent ranges, such as differences of approximately a few percent.

[0022] (Implementation Method)

[0023] [constitute]

[0024] First, the metal wire and the metal mesh having the metal wire in the embodiment will be described using FIG1.

[0025] Figure 1 is a schematic diagram of a metal mesh 20 incorporating the metal threads 10 of this embodiment. In Figure 1, the mesh is schematically shown only in a portion of the metal mesh 20, but the metal mesh 20 as a whole is mesh-like. The metal mesh 20 has multiple metal threads 10, each serving as both warp and weft yarns. That is, the metal mesh 20 is manufactured by weaving multiple metal threads 10, each serving as either warp or weft yarn.

[0026] The metal mesh 20 is, for example, a screen used in screen printing. The metal mesh 20 has a plurality of openings 22. The openings 22 are the portions that allow ink to pass through in screen printing. By blocking a portion of the openings 22 with an emulsion or resin (e.g., polyimide), non-passing portions are formed where ink cannot pass through. By patterning the shape of the non-passing portions into arbitrary shapes, it becomes possible to screen print in the desired shape.

[0027] When the metal mesh 20 is used for screen printing, the reduction in diameter of the metal wire 10 progresses in stages due to the improved precision of screen printing. With this reduction, the cross-sectional area of ​​the metal wire 10 decreases, and consequently, the absolute strength decreases significantly. For example, the tensile strength of a typical 13μm tungsten wire is 3.4 GPa, and the absolute strength is 0.45 N. In contrast, for a 11μm tungsten wire with a reduced diameter, the absolute strength decreases to 0.32 N. To compensate for the decrease in absolute strength, an increase in strength per unit cross-sectional area, i.e., tensile strength, is required. For example, for a 11μm diameter metal wire 10, a tensile strength of 4.8 GPa or higher is required.

[0028] Metal wire 10 is a tungsten wire made of tungsten (W) or a tungsten alloy wire made of tungsten alloy. The tungsten content is 75% by mass or more. The tungsten content can also be 80% by mass or more, 85% by mass or more, 90% by mass or more, 95% by mass or more, 99% by mass or more, 99.9% by mass or more, or 99.99% by mass or more.

[0029] It should be noted that the tungsten content is the ratio of tungsten to the weight of metal wire 10. The same applies to the content of other elements such as rhenium (Re) and potassium (K), which will be discussed later. In addition, metal wire 10 may also contain unavoidable impurities that are inevitably introduced during manufacturing.

[0030] Tungsten alloys are, for example, rhenium-tungsten alloys (ReW alloys). The rhenium content is, for example, 0.1% to 10% by mass. The rhenium content can also be 0.5% by mass or more, or 1% by mass or more. Furthermore, the rhenium content can also be 5% by mass or more.

[0031] A high rhenium content increases the tensile strength of the metal wire 10. However, an excessively high rhenium content makes it difficult to maintain a high tensile strength while thinning the wire. Specifically, wire breakage becomes more likely, making it difficult to draw long strips. By reducing the rhenium content and setting the tungsten content to 90% by mass or more, the processability of the metal wire 10 can be improved. Furthermore, by reducing the content of rare and expensive rhenium, it becomes possible to mass-produce inexpensive metal wires 10 in long strips.

[0032] The wire diameter of the metal wire 10 is 13 μm or less. The smaller the wire diameter, the higher the aperture ratio of the metal mesh 20 can be manufactured, which, for example, improves printing accuracy. The wire diameter of the metal wire 10 can also be 12 μm or less, 10 μm or less, 8 μm or less, or 7 μm or less. The wire diameter of the metal wire 10 can be, for example, 5 μm or more, but is not limited to these.

[0033] The diameter of the metal wire 10 is not uniformly less than 1.0 μm. Diameter non-uniformity is equivalent to the absolute value of the difference between the maximum and minimum diameter of the metal wire 10. Therefore, the difference in diameter between any two points on the metal wire 10 is less than 1.0 μm. Diameter non-uniformity can be measured, for example, using a laser wire diameter measuring machine, SEM (Scanning Electron Microscope), or laser microscope. The diameter non-uniformity can also be less than 0.6 μm, less than 0.5 μm, less than 0.4 μm, or less than 0.3 μm.

[0034] Furthermore, the cross-sectional shape of the metal wire 10 at the section orthogonal to the wire axis is, for example, circular, but not limited to this. The cross-sectional shape of the metal wire 10 can also be elliptical, square, or rectangular, etc.

[0035] The tensile strength of the metal wire 10 is 4.8 GPa (=4800 MPa) or higher. The tensile strength can also be 4.9 GPa or higher, 5.0 GPa or higher, 5.1 GPa or higher, or 5.2 GPa or higher. The tensile strength can be determined, for example, based on the tensile test of the Japanese Industrial Standard (JIS H 44608).

[0036] The straightness of the metal wire 10 is expressed as the natural sag length per 1000 mm. Specifically, the natural sag length (i.e., straightness) of the metal wire 10 per 1000 mm is 800 mm or more. The straightness of the metal wire 10 can also be 900 mm or more, 950 mm or more, or 970 mm or more. The natural sag length can be measured, for example, based on the straightness test of the Japanese Industrial Standard (JIS H 4460 15).

[0037] As described above, the metal wire 10 of this embodiment has a small wire diameter and high tensile strength and straightness. In addition, it has a high tungsten content and excellent processability.

[0038] [Manufacturing Method]

[0039] Next, the manufacturing method of the metal wire 10 will be described using Figures 2A and 2B. Figure 2A is a flowchart showing the manufacturing method of the metal wire 10 according to this embodiment. Figure 2B is a flowchart showing another example of the manufacturing method of the metal wire 10 according to this embodiment.

[0040] As shown in Figure 2A, firstly, tungsten ingot material is prepared (S10). Specifically, an aggregate of tungsten powder is prepared, and tungsten ingot material is produced by pressing and sintering the prepared aggregate.

[0041] It should be noted that, in the case of manufacturing the metal wire 10 made of tungsten alloy, a mixture of tungsten powder and metal powder (e.g., rhenium powder) in a specified ratio is prepared to replace the aggregate of tungsten powder. The average particle size of the tungsten powder and rhenium powder is, for example, in the range of 3 μm to 4 μm, but is not limited thereto.

[0042] Next, the tungsten ingot is forged (S12). Specifically, the tungsten ingot is stretched by forging and compressing it from all sides, thereby forming a wire-shaped tungsten wire. Rolling can also be performed instead of forging.

[0043] For example, tungsten ingots with a diameter of approximately 15 mm to 25 mm are formed into tungsten wires with a diameter of approximately 3 mm through repeated die forging. Annealing is performed midway through the die forging process to ensure machinability in subsequent processing. For example, annealing at 2400°C is performed for wires with a diameter of 8 mm to 10 mm. However, to ensure tensile strength resulting from grain refinement, annealing is not performed in die forging processes with wire diameters below 8 mm.

[0044] Next, the tungsten wire is heated at 900°C (S14) before heat drawing. Specifically, the tungsten wire is heated directly using a burner or the like. By heating the tungsten wire, an oxide layer is formed on its surface to prevent breakage during subsequent heat drawing.

[0045] Next, heated wire drawing (S16) is performed. Specifically, tungsten wire is drawn (refined) while heated using one or more drawing dies. The heating temperature is, for example, 1000°C. It should be noted that the higher the heating temperature, the better the machinability of the tungsten wire, and therefore the easier it is to draw. The heated wire drawing is performed repeatedly while changing the drawing die. The reduction in cross-sectional area of ​​the tungsten wire produced by one drawing using one drawing die is, for example, 10% to 40%. A lubricant obtained by dispersing graphite in water can also be used in the heated wire drawing process.

[0046] The heating and drawing process is repeated until the desired tungsten wire is obtained (S18 is "No"). The desired wire diameter here is the wire diameter when the number of drawing cycles is reduced to 2, for example, about 80 μm.

[0047] It should be noted that during the repeated heating and drawing processes, a drawing die with a smaller aperture than the one used in the previous drawing is used. Furthermore, during these repeated heating and drawing processes, the tungsten wire is heated to a lower temperature than the previous drawing temperature. That is, the heating temperature decreases in stages. The final heating temperature, for example, is 400°C, which helps to refine the crystal grains.

[0048] With the desired tungsten wire diameter obtained and two remaining drawing cycles ("Yes" in S18), room temperature drawing is performed (S20). It should be noted that, as shown in Figure 2B, electrolytic grinding (S19) can also be performed before room temperature drawing (S20). In room temperature drawing, the tungsten wire is drawn without heating, thereby achieving further refinement of the crystal grains. Furthermore, room temperature drawing also has the effect of aligning the crystal orientation in the processing axis direction (specifically, the direction parallel to the axis of the metal wire 10).

[0049] "Room temperature" refers to a temperature range of 0°C to 50°C, with 30°C as an example. Specifically, multiple drawing dies with different apertures are used to draw tungsten wire. In room temperature drawing, a water-soluble liquid lubricant is used. Since no heating is performed in room temperature drawing, liquid evaporation is suppressed. Therefore, the liquid lubricant can function effectively. Compared to traditional tungsten wire processing methods that involve heating and drawing at temperatures above 600°C, this method, by processing the tungsten wire without heating and simultaneously cooling it with a liquid lubricant, suppresses dynamic recovery and recrystallization, prevents wire breakage, promotes crystal grain refinement, and achieves high tensile strength.

[0050] The processing rate in room temperature drawing is, for example, over 70%. The processing rate is expressed by the following formula (1), using the wire diameter Db before room temperature drawing and the wire diameter Da immediately after room temperature drawing.

[0051] (1) Processing rate = {1 - (Da / Db)} 2}×100

[0052] As can be seen from equation (1), the greater the reduction in wire diameter through room temperature drawing, the higher the processing rate becomes. For example, even if the wire diameter Db before room temperature drawing is the same, the higher the processing rate, the smaller the wire diameter Da becomes after room temperature drawing. By increasing the processing rate, the degree of thinning of the tungsten wire resulting from room temperature drawing increases, thus obtaining finer tungsten wire. The processing rate of room temperature drawing is 70% or higher, but it can also be 80% or higher, 90% or higher, or even 95% or higher. The wire diameter after room temperature drawing is approximately in the range of 20 μm to 40 μm.

[0053] Next, after room temperature drawing, low-temperature hot drawing (S22) is performed. That is, the final drawing of the tungsten wire is carried out while heating at a low temperature. The temperature at this point is higher than the room temperature drawing temperature (S20) but lower than the hot drawing temperature (S16). Specifically, the low-temperature hot drawing temperature is in the range of 100℃ to 300℃, for example, 200℃ or 300℃. The wire diameter after low-temperature hot drawing is approximately in the range of 10μm to 16μm.

[0054] Normally, processing is carried out at a heating temperature of 500°C to 600°C, while low-temperature hot drawing is a new processing method that lowers the temperature by about 300°C. This can improve tensile strength and straightness or wire diameter uniformity. On the other hand, if the wire is drawn at room temperature and then processed at 500°C to 600°C, the tensile strength decreases and does not reach 4.8 GPa (Comparative Example 27 in Table 2 below).

[0055] Finally, for the tungsten wire formed by low-temperature hot drawing, electrolytic polishing (S24) is performed to finely adjust the diameter. Electrolytic polishing is performed, for example, by impregnating the tungsten wire and the counter electrode in an electrolyte such as an aqueous sodium hydroxide solution to create a potential difference between the tungsten wire and the counter electrode. The wire diameter after electrolytic polishing is 13 μm or less.

[0056] The metal wire 10 of this embodiment is manufactured through the above processes. The length of the metal wire 10 manufactured through the above processes is, for example, 50 km or more, and it can be used in industry. The metal wire 10 can also be cut into suitable lengths according to the method used, and used in the shape of a needle or a rod.

[0057] It should be noted that the various processes shown in the manufacturing method of metal wire 10 are performed in series (assembly line). Specifically, the multiple wire drawing dies used in step S16 are arranged on the production line in order of decreasing aperture. Furthermore, a heating device such as a burner is arranged between each wire drawing die. Additionally, an electrolytic polishing device may be arranged between each wire drawing die. Downstream of the wire drawing die used in step S16 (towards subsequent processes), one or more wire drawing dies used in step S20 and one or more wire drawing dies used in step S22 are arranged in order of decreasing aperture, and an electrolytic polishing device is arranged downstream of the wire drawing die with the smallest aperture. It should be noted that each process can also be performed individually.

[0058] Furthermore, the manufacturing method of the metal wire 10 described above is just one example, and the temperature and wire diameter in each process can be adjusted appropriately.

[0059] As described above, in the manufacturing method of the metal wire 10 of this embodiment, after heating and drawing at a first temperature (high temperature), drawing at room temperature at a second temperature (room temperature), and then heating and drawing at a low temperature at a third temperature (low temperature). The third temperature is higher than the second temperature (room temperature) and lower than the first temperature (high temperature).

[0060] In this way, the metal wire 10 is manufactured by performing a new process such as low-temperature hot drawing (also known as low-temperature heat treatment). By performing low-temperature hot drawing, a metal wire 10 with a small wire diameter and a wire diameter deviation of less than 1.0 μm, as well as high tensile strength and straightness, is achieved.

[0061] [Example]

[0062] Hereinafter, a comparison will be made with a metal wire manufactured without low-temperature hot drawing, and several embodiments of the metal wire 10 of this embodiment will be described using Table 1 and Figures 3 and 4.

[0063] Table 1 below shows the material, processing method (drawing method), wire diameter, tensile strength, straightness (natural droop length per 1000 mm), and wire diameter unevenness of examples and comparative examples of metal wires made of tungsten or tungsten alloys.

[0064] [Table 1]

[0065]

[0066] [Table 2]

[0067]

[0068] The relationship between straightness and tensile strength in the embodiments shown in Table 1 and the comparative examples shown in Table 2 is illustrated in Figure 3. Figure 3 is a graph showing the relationship between the straightness and tensile strength of the metal wire 10 of this embodiment. In Figure 3, the horizontal axis represents the straightness of the metal wire 10 (natural droop length per 1000 mm), and the vertical axis represents the tensile strength of the metal wire 10.

[0069] Furthermore, the relationship between wire diameter unevenness and tensile strength in each embodiment shown in Table 1 and each comparative example shown in Table 2 is illustrated in Figure 4. Figure 4 is a graph showing the relationship between wire diameter unevenness and tensile strength of the metal wire 10 in this embodiment. In Figure 4, the horizontal axis represents the wire diameter unevenness of the metal wire 10, and the vertical axis represents the tensile strength of the metal wire 10. In addition, in Figures 3 and 4, the numbers marked next to the plotted points represent the numbers of each of the embodiments 1 to 14 in Table 1 and the comparative examples 21 to 28 in Table 2.

[0070] Examples 1 to 14 are all metal wires manufactured according to the flowchart shown in Figure 2A. Examples 1 to 14 are metal wires obtained by performing both room temperature drawing (S20) and low temperature hot drawing (S22) while appropriately adjusting the processing conditions such as material, target value of wire diameter, processing rate of room temperature drawing and temperature of low temperature hot drawing.

[0071] Comparative Examples 21 and 22 are metal wires manufactured after room temperature drawing (S20) without low-temperature hot drawing (S22). It was found that, as shown in Table 2 and Figure 3, while room temperature drawing resulted in high tensile strength, it also resulted in low straightness. Furthermore, it was found that, as shown in Figure 4, the wire diameter was highly uneven and the straightness was low.

[0072] Comparative Examples 23-26 are metal wires manufactured without either room temperature drawing (S20) or low-temperature hot drawing (S22). As shown in Table 2 and Figures 3 and 4, high tensile strength cannot be obtained without room temperature drawing. To improve tensile strength, a room temperature drawing process is required, but in this case, the flatness decreases as in Comparative Examples 21 and 22.

[0073] Furthermore, Comparative Example 27 involved a metal wire that underwent room temperature drawing (S20) followed by conventional hot drawing at 500°C to 600°C instead of low-temperature hot drawing (S22). As shown in Table 2 and Figure 3, while high flatness was achieved, the tensile strength did not reach 4.8 GPa.

[0074] In this way, without low-temperature hot drawing, it is impossible to simultaneously achieve high tensile strength and high straightness. As with the comparative example metal wire, in fine metal wires with a diameter of less than 13 μm, there is an inverse relationship between tensile strength and straightness. That is, if tensile strength is increased, straightness decreases, and vice versa.

[0075] In contrast, as shown in Table 1 and Figure 3, high tensile strength and high straightness were achieved in Examples 1 to 14. Furthermore, as shown in Figure 4, high tensile strength and small wire diameter inconsistencies or high straightness were achieved. That is, by performing low-temperature hot drawing, metal wire 10 that balances high tensile strength and high straightness can be obtained even when the wire diameter is as small as 13 μm or less. Since metal wire 10 is a rhenium-free tungsten wire or a rhenium-tungsten alloy wire with a rhenium content of 10% by mass or less, it exhibits excellent machinability.

[0076] Furthermore, Examples 1-6 are rhenium-tungsten alloy wires containing 1% rhenium by mass, and Examples 7-14 are tungsten wires without rhenium. As can be seen from Table 1, when compared under the same wire diameter and the same drawing conditions, the tensile strength of the rhenium-tungsten alloy wire is slightly higher than that of the tungsten wire. This is based on the solid solution strengthening mechanism. In addition, the dispersion strengthening precipitated at the grain boundaries in the form of oxides also contributes to a certain degree of increase in tensile strength.

[0077] Therefore, as an element exhibiting such a strengthening mechanism, the same effect can be obtained by using other metallic elements with different atomic radii to replace rhenium. That is, when the metal wire 10 is made of a tungsten alloy, the metal contained in the tungsten alloy does not have to be rhenium. That is, the tungsten alloy can also be an alloy of tungsten with one or more metals other than tungsten.

[0078] Metals other than tungsten include transition metals such as molybdenum (Mo), iridium (Ir), ruthenium (Ru), or osmium (Os), which have atomic radii close to rhenium. The content of these metals is, for example, 0.1% to 10% by mass, but is not limited to this. For example, the content of these metals in tungsten alloys can be less than 0.1% by mass or greater than 1% by mass.

[0079] Furthermore, as observed by comparing Examples 3 and 4, by lowering the temperature of low-temperature hot drawing, tensile strength can be improved while maintaining high straightness, even with the same wire diameter. As observed by comparing Examples 3 and 5, by increasing the processing rate of room-temperature drawing, tensile strength can be improved while maintaining high straightness, even with the same wire diameter. The same relationship exists in rhenium-free tungsten wire, as observed by comparing Examples 9 to 14.

[0080] Furthermore, as is known from comparing Examples 3 and 4, by increasing the temperature of the low-temperature hot drawing, even with the same wire diameter, it is possible to improve straightness while maintaining high tensile strength. The same relationship exists in rhenium-free tungsten wire, as is known from comparing Examples 9 to 14.

[0081] [Effects, etc.]

[0082] As described above, the metal wire 10 in this embodiment is made of tungsten or a tungsten alloy, has a wire diameter of 13 μm or less, a tensile strength of 4.8 GPa or more, and a natural droop length of 800 mm or more per 1000 mm. Furthermore, for example, the wire diameter is not always 1.0 μm or less.

[0083] This enables the production of metal wires 10 with small diameters and excellent tensile strength and straightness.

[0084] Furthermore, as a treatment to improve straightness, annealing straightening, which involves heating the wire at a high temperature of around 1000°C after drawing or electrolytic grinding, is generally known. However, for example, when the metal wire of Comparative Example 21 was subjected to annealing straightening, although the straightness was improved, the tensile strength decreased. For example, Comparative Example 28 in Table 2 is an example of annealing straightening of the metal wire of Comparative Example 21. As can be seen from the comparison with Comparative Example 21, although the straightness can be improved by annealing straightening, the tensile strength is reduced to below 4.8 GPa instead. That is, in terms of annealing straightening, it is impossible to achieve both high straightness and high tensile strength. In addition, since the wire diameter unevenness does not change much during annealing straightening, it is impossible to reduce the wire diameter unevenness.

[0085] In contrast, the metal wire 10 in this embodiment is a metal wire that has not undergone annealing and straightening treatment. Even without annealing and straightening treatment, high straightness and high tensile strength can be achieved through low-temperature hot drawing.

[0086] In addition, for example, the natural hanging length is more than 900mm per 1000mm.

[0087] Therefore, due to the improved flatness, it is more useful for weaving metal mesh 20, etc.

[0088] If metal threads with a diameter variation exceeding 1.0 μm are used for weaving, uneven weaving can easily occur. Consequently, the height of the metal mesh resulting from this uneven weaving may also become uneven. When this metal mesh is used for screen printing, problems such as reduced screen printing accuracy can arise during pressing with a squeegee or similar tool.

[0089] Furthermore, using metal wire with a straightness of less than 800mm for weaving can cause the following problems: thread twisting and breakage during weaving. Using metal wire with a straightness of less than 800mm for secondary processing of the thread other than weaving, such as twisting, can also cause thread breakage and other problems.

[0090] In contrast, the metal mesh 20 of this embodiment includes metal threads 10 as warp or weft yarns. Furthermore, the metal mesh 20 can be used, for example, as a screen printing mesh.

[0091] Therefore, by utilizing the metal wire 10 with its small diameter and excellent tensile strength and straightness, the metal mesh 20 can be easily manufactured. Due to the small wire diameter, a metal mesh 20 with a high opening ratio can be manufactured.

[0092] In addition, for example, the tungsten content can be above 90% by mass.

[0093] Thus, for example, by reducing the content of other elements such as rhenium and increasing the content of tungsten, it is possible to achieve a metal wire 10 with excellent processability.

[0094] (other)

[0095] The metal wire and metal mesh of the present invention have been described above based on the embodiments, but the present invention is not limited to the above embodiments.

[0096] For example, the above embodiment shows an example where the metal mesh 20 is a wire mesh, but it is not limited to this. The metal mesh 20 can also be used in filters or protective clothing, etc. All the warp and weft yarns of the metal mesh 20 can be metal wires 10, or at least one warp or weft yarn can be a metal wire 10, and the remaining warp or weft yarns can be other metal wires such as stainless steel wire.

[0097] Furthermore, for example, the metal wire 10 can also be used in applications other than the thread used in the weaving of the metal mesh 20. For example, the metal wire 10 can also be used as saw wire, medical needle, rope, or cord.

[0098] Furthermore, for example, the tungsten content in the metal wire 10 may be less than 75% by mass, or even less than 70% by mass.

[0099] Furthermore, for example, the metal wire 10 can also be made of tungsten doped with potassium (K). The doped potassium is present at the grain boundaries of the tungsten crystals. The potassium (K) dispersed at the grain boundaries suppresses crystal coarsening during high-temperature heating and hot wire drawing. However, since no crystal coarsening occurs during processing in room-temperature wire drawing, the amount of potassium (K) can be, for example, less than 0.010% by mass. On the other hand, it has the effect of slightly increasing the strength in the process up to room-temperature wire drawing. Even potassium-doped tungsten wire can achieve a tungsten wire with a higher tensile strength than the general tensile strength of piano wire, just like in the case of tungsten alloy wire. It is not limited to potassium oxides; even oxides of other substances such as cerium or lanthanum can achieve the same effect.

[0100] Potassium-doped tungsten wires can be manufactured by using potassium-doped tungsten powder instead of tungsten powder, and by the same manufacturing method as in the embodiments.

[0101] In addition, for example, an oxide film or nitride film or a coating may be applied to the surface of the metal line 10.

[0102] Furthermore, the following methods are also included in this invention: methods obtained by implementing various modifications to each embodiment as conceived by those skilled in the art; methods implemented by arbitrarily combining the constituent elements and functions of each embodiment without departing from the spirit of this invention.

[0103] Explanation of symbols

[0104] 10 Metal wire

[0105] 20 Metal Mesh

Claims

1. A metal wire made of tungsten or a tungsten alloy, wherein the wire diameter is less than 13 μm, the tensile strength is greater than 4.8 GPa, and the natural droop length per 1000 mm is greater than 800 mm.

2. The metal wire according to claim 1, wherein the wire diameter is not all below 1.0 μm.

3. The metal wire according to claim 1 or 2, wherein the natural hanging length per 1000 mm is 900 mm or more.

4. The metal wire according to claim 1 or 2, wherein, The tungsten content is over 90% by mass.

5. A metal mesh comprising the metal wires as warp or weft yarns according to any one of claims 1 to 4.

6. The metal mesh according to claim 5, which is used as a screen printing mesh.

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