Designing of metal wire and method for manufacturing same

Abstract

[Problem] The present invention provides a metal wire which reduces damage to processing equipment caused by a tungsten wire and is not likely to be broken in a bending process. In addition, the purpose of the present invention is to provide: a metal wire which has a smaller diameter, high bending strength, and high tensile strength; and a method for producing the metal wire. [Solution] A metal wire that contains tungsten as a main component is used as a core material, a plating layer that contains either copper or zinc, or both copper and zinc is formed on the surface, and wire drawing is repeated, thereby providing a specific outer diameter, strength of the plating layer, and strength against bending. By having the surface provided with a plating layer that contains either copper or zinc, or both copper and zinc, damage to equipment for processing a metal wire, such as a loom, can be significantly reduced. In addition, in order to further reduce the outer diameter, high tensile strength and bending strength capable of withstanding bending are obtained by a manufacturing method including removal of plating or the like.

Description

Relates to a method for designing and manufacturing a metal wire.

[0001] The present invention relates to a metal wire provided with plating on a core material containing tungsten as a main component, and a method for manufacturing a thinner metal wire developed therefrom.

[0002] Patent Document 1 describes a technique for improving the surface roughness of a tungsten wire and suppressing the wear of a loom, which is processing equipment for manufacturing a metal mesh. However, in recent years, due to the increase in the number of meshes accompanying high definition, the contact between the processing equipment and the metal wire has increased, and it is presumed that equipment wear is remarkable.

[0003] Patent Document 2 describes a technique in which an oxide layer with a predetermined thickness is formed on the surface of a tungsten wire, and the wear of the processing equipment is reduced to about one-third.

[0004] Patent Document 3 is about measures taken on the equipment side of the loom. In order to suppress the wear of the reed, which is a part of the loom equipment, a hard plating is formed on the reed, and a technique for reducing the wear to about one-third is described. It is presumed that it is less feasible from the viewpoint of the accuracy degradation of the reed and the cost of the hard plating.

[0005] Patent Document 1: Patent No. 6213934 Patent Document 2: WO2023 / 153089A1 Patent Document 3: Patent No. 6210471

[0006] Metal wires containing tungsten as a main component are expanding their usage due to their high elastic modulus and strength. At the same time, because of their high surface hardness, wear of the parts in contact with the tungsten wire becomes a problem in equipment for secondary processing of tungsten wires. For example, in the manufacture of metal meshes, especially for high-precision parts called reeds, replacement or stoppage due to wear becomes a major problem in manufacturing. Therefore, an object of the present invention is to provide a metal wire capable of suppressing wear of equipment or parts. Another problem is miniaturization. Based on the present invention, it is possible to remove the plating after mesh processing to achieve miniaturization, but it is also possible to remove the plating at the time of the metal wire containing tungsten as a main component, process the outer diameter to a smaller diameter, and further achieve further miniaturization by etching or the like after mesh processing. At that time, the tensile strength, bending strength, porosity, and straightness of the metal wire become problems.

[0007] A metal wire according to one aspect of the present invention has a metal wire mainly composed of tungsten as a core material, and its surface is provided with a plating layer containing copper, zinc, or both copper and zinc. The thickness of the plating layer is 0.2% or more and 10% or less of the diameter of the core material mainly composed of tungsten.

[0008] A manufacturing method according to one aspect of the present invention is a manufacturing method in which a metal wire mainly composed of tungsten is used as a core material, and a plating layer containing copper, zinc, or both copper and zinc is provided on the surface, wherein the thickness of the plating layer is 0.2% or more and 5% or less of the diameter of the core material mainly composed of tungsten, and the manufacturing method includes a step of removing part or all of the plating layer after the wire drawing process.

[0009] A metal mesh according to one aspect of the present invention comprises the metal wire according to the above aspect as warp threads or weft threads.

[0010] According to the present invention, in metal wires designed to retain plating, wear on equipment or parts can be reduced to less than one-tenth that of conventional tungsten wires. Furthermore, by controlling the thickness of the plating layer within a certain range and performing wet drawing, metal wires from which the plating layer has been removed can be obtained with a smaller diameter, higher tensile strength, higher bending strength, and good straightness.

[0011] Figure 1 is an explanatory diagram of the manufacturing process of a conventional tungsten wire. Figure 2 is an explanatory diagram of the manufacturing process of the metal wire of the present invention. Figure 3 is an explanatory diagram of the manufacturing process of the metal wire of the present invention. Figure 4 is an explanatory diagram of the manufacturing process of the metal wire of the present invention. Figure 5A is a cross-sectional SEM image of the core material of Example 5 of the present invention, and the void ratio was evaluated. Figure 5B is a cross-sectional SEM image of the core material of Example 6 of the present invention, and the void ratio was evaluated. Figure 6A is a cross-sectional SEM image of the core material of Example 1 of the present invention, and the void ratio was evaluated. Figure 6B is a cross-sectional SEM image of the core material of Example 3 of the present invention, and the void ratio was evaluated.

[0012] The core material of the metal wire according to this embodiment is a metal wire containing tungsten as its main component. "Main component" means that the element content is greater than 50 mass%. For example, the tungsten content is 90 mass% or more, but it may be 95 mass% or more, 99 mass% or more, or 99.8 mass% or more. Also, for example, it may be 99.9% or more, or 99.99% or more.

[0013] The core material of the metal wire may contain additive elements. Specifically, potassium. Rare earth elements such as lanthanum and cerium may also be added. Transition metals such as rhenium may also be added. The amount of potassium added is 0.001 mass% or more. The amount of potassium added may be 0.003 mass% or more, or 0.005 mass% or more. The upper limit for the amount of potassium added is, for example, 0.009 mass% or less. If the amount of potassium added is too high, it becomes brittle and the workability deteriorates. The amount of rare earth elements such as lanthanum and cerium added is 0.02 mass% or more. The amount of rare earth elements such as lanthanum and cerium added may be 0.03 mass% or more, or 0.05 mass% or more. The amount of rare earth elements such as lanthanum and cerium added may be, for example, 0.1 mass% or more, or 0.2 mass% or more. The upper limit for the amount of rare earth elements such as lanthanum and cerium added is 0.8 mass% or less. If the amount added is too high, the material becomes hard and its workability deteriorates. Metal wires may contain unavoidable elements that are mixed in during the manufacturing process, such as iron, chromium, nickel, and molybdenum.

[0014] The outer diameter of the metal wire is 50 μm or less, but is not limited to this. The outer diameter of the metal wire may be 40 μm or less, 30 μm or less, or 20 μm or less. For example, the outer diameter of the metal wire may be 16 μm or less, 13 μm or less, 11 μm or less, or 9 μm or less. Furthermore, it may be 8 μm or less, and 7 μm or less is also achievable.

[0015] The outer diameter of the metal wire is 5 μm or more. The outer diameter of the metal wire may be 6 μm or more, or 7 μm or more. For example, the outer diameter of a metal wire that has had its plating removed and reduced in diameter is 3 μm or more. The outer diameter of the metal wire may be 4 μm or more, or 5 μm or more.

[0016] The tensile strength of the metal wire is 3500 MPa or higher. The tensile strength of the metal wire may also be 4000 MPa or higher, or 4500 MPa or higher. For example, the tensile strength of the metal wire may be 5000 MPa or higher, 5500 MPa or higher, or 6000 MPa or higher. High tensile strengths of 6500 MPa or higher are also achievable.

[0017] The straightness of the metal wire is 800 mm or more when measured using the hanging method for a 1000 mm length of wire. It may also be 850 mm or more, 900 mm or more, or 950 mm or more when measured using the hanging method for a 1000 mm length of wire.

[0018] [Manufacturing Process] Figure 1 shows the conventional manufacturing process for metal wires mainly composed of tungsten. Because tungsten wire is a high-melting-point metal, it is generally processed by dry drawing, in which an aqueous solution of dispersed carbon is applied to the wire, dried in a heating furnace, and the carbon is turned into a powder, and the wire is processed with a die while still heated.

[0019] In the manufacturing process shown in Figure 1, dry drawing is repeated to finish the outer diameter to a predetermined size. The outer diameter and straightness are adjusted at the final diameter of the dry drawing process. After this, electrolytic polishing removes the oxide and carbon layers from the circumference and adjusts the outer diameter to the desired size. At this time, electrolytic polishing polishes the tungsten on the circumference, which changes the internal stress state and worsens the straightness. Therefore, a straightening process is added in the final step to improve the straightness to the predetermined level.

[0020] Figure 2 shows the manufacturing process for metal wire according to the present invention. The manufacturing process is the same as in Figure 1 up to the outer diameter, but for example, if the final outer diameter is 20 μm, electropolishing is performed at 40 μm. After electropolishing, a plating layer is formed. The plating layer may be formed by electrolytic plating or electroless plating. A base plating of nickel or the like may be provided to improve the adhesion between tungsten and the plating layer.

[0021] After forming the plating layer, wet wire drawing is performed using a liquid lubricant. In conventional wet wire drawing using tungsten as the main component, die wear was a problem because the tungsten directly contacted the wire drawing die. In this invention, die wear can be reduced because there is a plating layer of copper, zinc, or copper and zinc on the surface. Furthermore, the straightness of the wire can be easily adjusted by performing wet wire drawing.

[0022] The final thickness of the plating layer depends on the thickness during plating formation and the degree of processing up to the final wire diameter. The thickness of the plating layer relative to the diameter of the core material is 0.2% or more, but it may be 1% or more, or even 2% or more. However, if the thickness of the plating layer relative to the diameter of the core material becomes too large, compressive stress will not be applied to the center of the tungsten wire core material during wet drawing, creating a void and making it prone to breakage during secondary processing. For this reason, the thickness of the plating layer relative to the diameter of the core material is 10% or less. When the outer diameter is made smaller, the thickness of the plating layer relative to the diameter of the core material is preferably 5% or less, and may also be 3% or less.

[0023] Figure 3 shows a manufacturing method for removing plating after the process shown in Figure 2. The plating removal method is carried out using a chemical solution. Specifically, the metal wire is continuously passed through a plating removal chemical solution while being rewound to remove the plating. Similarly, the plating may be removed by electrolytic stripping while the metal wire is being rewound. Plating may also be removed by a combination of oxidative heating and electrolytic stripping. Diameter reduction is achieved by removing the plating. For example, if the plating is removed from a metal wire with an outer diameter of 11 μm, a metal wire with an outer diameter of 10 μm is obtained.

[0024] Figure 4 shows a manufacturing method that achieves further diameter reduction by performing electropolishing after the process in Figure 3. Electropolishing is a method in which opposing electrodes are placed in a tank containing an alkaline solution, and the metal wire is continuously passed through the solution to electrically abrade the surface. By electropolishing, for example, a metal wire with an outer diameter of 10 μm can be reduced to an outer diameter of 8 μm.

[0025] The void ratio of the core material cross-section is 1% or less. The void ratio of the core material cross-section may be 0.7% or less, or 0.4% or less.

[0026] [Examples and Comparative Examples] To evaluate wear on equipment caused by metal wire, the metal wire was repeatedly pressed against a metal plate under evaluation at predetermined tension, speed, and angle, and the wear depth of the metal plate was measured. The metal plate used was a commonly used high-carbon steel SK material. The wear was evaluated and calculated using an index where the wear amount of a conventional tungsten wire without plating was set to 1.0.

[0027] As an evaluation method for bending, a jig was prepared to create a bending radius of half the wire diameter for the metal wire. The metal wire was then folded 180 degrees and subjected to a tensile test. The strength until breakage was measured, and the ratio of the 180-degree bending strength to the tensile strength was calculated. This evaluation of bending serves as an indicator of wire breakage during secondary processing. A ratio of 180-degree bending strength to tensile strength of the metal wire of 0.5 or higher is desirable, and 0.6 or higher is even more desirable. For example, if the ratio is 0.7 or higher, secondary processing can be performed even with larger bends without wire breakage. Since the manufacturing loss due to wire breakage during secondary processing is large, the ability to process without wire breakage is an important indicator.

[0028] Comparative Example 1 in Table 1 was processed to an outer diameter of 13 μm according to the conventional process shown in Figure 1. Examples 1 to 4 and Comparative Examples 2 and 3 were processed to an outer diameter of 13 μm by forming a plating layer of a predetermined thickness according to the process shown in Figure 2, and then subjected to wear evaluation, bending evaluation, and other evaluations. Table 1: Examples and Comparative Examples

[0029] Examples 1 to 4 and Comparative Example 3 show good results when the plating layer thickness relative to the core material diameter is 0.2% or more and 15% or less, resulting in wear on the high-carbon steel SK material being less than one-tenth of that of the unplated material. However, in Comparative Example 3, the 180-degree bending strength relative to the tensile strength was 0.47, and wire breakage occurred during secondary processing. This is because the plating thickness in Comparative Example 3 was too thick, preventing compressive stress from being applied to the center of the tungsten core material, resulting in the formation of voids inside the core material and a high porosity. A more appropriate upper limit for the plating layer thickness relative to the core material diameter is 10%.

[0030] In Comparative Example 2, the plating layer thickness relative to the core material diameter was 0.1%, and the wear of the high-carbon steel SK material was about one-fifth that of the unplated material, indicating that the effect on wear resistance was not significant. A more appropriate lower limit for the plating layer thickness relative to the core material diameter is 0.2%.

[0031] Examples 1 to 4 and Comparative Examples 2 and 3 were metal wires manufactured using the process shown in Figure 2. Compared to Comparative Example 1, which was manufactured using the process in Figure 1, the hanging length was 900 mm or more, indicating a better result. This is because the final wire drawing method is wet wire drawing of metal wires with a plating layer, which eliminates internal stress changes caused by carbon powder clogging in conventional processes. The improved straightness makes handling the metal wires easier in secondary processing, leading to increased productivity.

[0032] Examples 1 to 4 showed better results with higher tensile strength compared to Comparative Example 1. This is because the wire drawing process is performed while cooling the die during the wet drawing process, which suppresses dynamic recrystallization and dynamic recovery caused by die heat generation during processing. The high tensile strength allows for a thinner outer diameter of the metal mesh wires, thus enabling the provision of a higher-resolution metal mesh.

[0033] Based on the experimental results described above, Examples 1 to 4 are embodiments that suppress equipment wear while ensuring the necessary bending strength.

[0034] Table 2 evaluates lines with further increased strength. Comparative Example 4 was processed to an outer diameter of 30 μm according to the conventional process shown in Figure 1, while Examples 5 and 6 were processed to an outer diameter of 30 μm after forming a plating layer of a predetermined thickness according to the process shown in Figure 2, followed by wear evaluation, bending evaluation, and other evaluations. Table 2: Examples and Comparative Examples

[0035] In Example 5, the amount of wear was 0.05 compared to Comparative Example 4, which was the same as the results in Table 1. The superiority against wear was confirmed by providing a plating layer regardless of the outer diameter or tensile strength.

[0036] The 180-degree bending strengths of Example 5 and Comparative Example 4 were at the same level as those of Example 2 and Comparative Example 1, which are under similar conditions in Table 1. The reason that the ratio of 180-degree bending strength to tensile strength is smaller than in Table 1 is that the tensile strength was higher, the pull-out stress increased, and the void ratio inside the core material became larger.

[0037] Figure 5A is a cross-sectional SEM image of Example 5, and Figure 5B is a cross-sectional SEM image of Example 6. Both images were taken at 50,000x magnification, and the porosity of the central part of the core material was evaluated by image processing. The porosity of Example 5 was 0.4%, and the porosity of Example 6 was 0.7%. A porosity of 1% or less is desirable, and 0.7% or less is even more desirable.

[0038] Table 3 shows the results of evaluating the tensile strength and straightness of Examples 1 to 4 of the metal wires in Table 1 after removing the plating according to the process in Figure 3, and further evaluating the tensile strength, straightness, and bending strength of Examples 1 to 4 and Comparative Example 1 after reducing their outer diameter to 9 μm by electropolishing. Table 3: Examples and Comparative Examples

[0039] In Examples 1 to 4, after plating removal, the tensile strength increased because the cross-sectional area of ​​the plating was eliminated. However, Example 4 had lower tensile strength than Examples 1 to 3. Furthermore, after electropolishing, Example 4 had a tensile strength that was more than 250 MPa lower than Examples 1 to 3. This is because the plating thickness was too thick, preventing compressive stress from being applied to the central part of the tungsten core material, resulting in lower strength in the central part of the core material. This difference in tensile strength was observed when the outer circumference was removed by electropolishing, leaving the central part. In other words, if Example 4 were electropolished to an even smaller outer diameter, the decrease in tensile strength would become even more pronounced. Therefore, the upper limit for the plating thickness is 5% of the core material diameter.

[0040] The straightness of Examples 1 to 3 after electrolytic polishing is good, maintaining the same level of straightness as after wire drawing or after plating removal, i.e., a hanging length of 950 mm or more. On the other hand, Comparative Example 1, produced using a conventional manufacturing process, had a hanging length of 880 mm after wire drawing, which is inferior to wet wire drawing, and further deteriorated to 860 mm after electrolytic polishing. Conventional manufacturing processes use dry wire drawing, which is prone to deterioration of straightness due to carbon clogging or changes in internal stress during electrolytic polishing caused by carbon clogging. Since workability in secondary processing is poor with a hanging length of less than 900 mm, a hanging length of 900 mm or more, more preferably 950 mm or more, is preferable.

[0041] Figure 6A is a cross-sectional SEM image of Example 1, and Figure 6B is a cross-sectional SEM image of Example 3. Both images were taken at 50,000x magnification, and the porosity of the central part of the core material was evaluated by image processing. The porosity of Example 1 was 0.2%, and the porosity of Example 3 was 0.4%. As a result of evaluation using the same method, the porosity of Example 4 was 0.7%, and the porosity of Comparative Example 3 was 1.2%. A porosity of 1% or less is desirable, and 0.7% or less is more preferable. Note that the porosity of the central part of the core material is the central part of the cross-section and is not affected by plating removal or electrolytic polishing.

[0042] Regarding the plating removal and electropolishing in Examples 1 to 4, not only are the tensile strength and straightness better than those in Comparative Example 1, which is a conventional manufacturing method, but the diameter can be reduced by removing the plating portion, and the amount of electropolishing of the metal wire mainly composed of tungsten is reduced, so it is also advantageous from the perspective of cost.

[0043] [Modification] Although the present invention has been described based on the above embodiments, the present invention is not limited to the described embodiments. For example, the same effects for the same purpose can be obtained with platings such as tin, nickel, silver, chromium, etc. That is, the effect can be obtained for all metal wires provided with plating and mainly composed of tungsten, without being limited to the type of plating.

[0044] For example, the plating layer may be removed after processing into a metal mesh. The plating layer is for performing wire drawing at low cost, obtaining a high-quality metal wire, and suppressing equipment wear during secondary processing, and the plating layer can be removed in the state of the mesh after secondary processing. By removing the plating layer after mesh processing, a mesh with a thinner outer diameter can be obtained.

[0045] The manufacturing process is not limited to FIGS. 2 to 4. Electropolishing may be performed after repeating wet wire drawing instead of dry wire drawing, a plating layer may be formed, and wet wire drawing may be performed. For example, it may be a metal wire on which a plating layer is formed after performing wire drawing and electropolishing on the final outer diameter. Also, correction processing may be performed in the final step of FIGS. 2 to 4 to improve straightness even more. In addition, forms obtained by applying modifications conceivable by those skilled in the art are also included in the present invention.

[0046] The plating removal method is not limited to the described method. The present invention is characterized by a series of manufacturing methods for obtaining a metal wire with a smaller diameter, high tensile strength, and good straightness by appropriately controlling the plating thickness and performing wet wire drawing to improve the characteristics of the core material, and by plating removal, or plating removal and electropolishing.

[0047] [Other] Although this document primarily describes the use of the metal wire as a metal mesh, the applications of the metal wire of this invention are not limited to metal mesh. Suppressing wear on equipment or preventing wire breakage due to bending when processing tungsten wire has been a long-standing challenge.

[0048] For example, it is used in stranded wires or bundled wires including ropes. The bundled wire may be composed solely of the metal wire of the present invention, or it may be composed in combination with other tungsten wires, stainless steel wires, copper wires, etc. Furthermore, by using the metal wire of the present invention in combination with copper wire, galvanic corrosion can be suppressed.

[0049] For example, it is used in knitted fabrics combined with synthetic fibers. Similarly, wear and tear on the parts of the knitted fabric that come into contact with the metal wire poses a manufacturing challenge.

Claims

1. A metal wire comprising a tungsten-containing metal wire as the main component as a core material, and having a copper plating layer, a zinc plating layer, or a plating layer containing both copper and zinc on its surface, wherein the thickness of the plating layer is 0.2% or more and 10% or less of the diameter of the core material, and the strength to break when the metal wire is bent 180 degrees at a bending radius of half the outer diameter of the metal wire and subjected to a tensile test is 0.5 or more compared to the tensile strength.

2. A metal wire comprising a tungsten-containing metal wire as a core material, and having a copper plating layer, a zinc plating layer, or a plating layer containing both copper and zinc on its surface, wherein the thickness of the plating layer is 0.2% or more and 10% or less of the diameter of the core material, and the void ratio of the cross-section of the core material is 1% or less.

3. The metal wire according to claim 1 or 2, wherein the outer diameter is 50 μm or less.

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

5. The metal wire according to claim 1 or 2, wherein the tensile strength is 3500 MPa or more.

6. A metal mesh comprising the metal wires of claim 1 or 2.

7. A method for manufacturing a metal wire containing tungsten as the main component according to claim 1 or 2, characterized by including a step of processing the metal wire while the thickness of the plating layer is 0.2% or more and 10% or less of the diameter of the core material.

8. A method for manufacturing a metal wire containing tungsten as the main component according to claim 1 or 2, characterized by comprising the steps of processing the metal wire such that the thickness of the plating layer is 0.2% or more and 5% or less of the diameter of the core material, and removing part or all of the plating layer after the processing.

9. A metal wire containing tungsten as the main component, having an outer diameter of 9 micrometers or less and a tensile strength of 4500 MPa or more, manufactured by the manufacturing method described in claim 8.

10. A metal mesh comprising the metal wire of claim 9.

Images