Tungsten wire

Abstract

To provide a tungsten wire 2 excellent in mechanical properties.SOLUTION: A material of a wire 2 is tungsten or a tungsten alloy. In the tungsten wire 2, a tensile strength is 4,600 MPa or more, and a ratio of 0.2% proof stress to the tensile strength is 80.0% or more. Preferably, in the tungsten wire 2, the 0.2% proof stress is 3,680 MPa or more and a breaking elongation is 2.0% or more. Preferably, a diameter of the tungsten wire 2 is 0.10 mm or less.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] This specification discloses a wire whose material is tungsten or a tungsten alloy. [Background technology]

[0002] The catheter has a mesh-like reinforcing layer. This reinforcing layer is formed by weaving a plurality of wires. Japanese Patent Application Laid-Open No. 3-286779 discloses a tungsten wire suitable for a catheter.

[0003] The contact probe has a probe pin. Japanese Patent Application Laid-Open No. 2005-249501 discloses a probe pin made of tungsten.

[0004] The wire saw device has a saw wire. JP 2020-105548 A discloses a saw wire made of tungsten. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 3-286779 [Patent Document 2] JP2005-249501A [Patent Document 3] Patent Publication No. 2020-105548 Summary of the Invention [Problem to be solved by the invention]

[0006] Catheters are required to be resistant to buckling inside a patient's body. Probe pins are required to have spring properties. Saw wires are required to be resistant to cutting during use. Tungsten wires are required to have excellent mechanical properties. It is the applicant's intention to provide a tungsten wire with excellent mechanical properties. [Means for solving the problem]

[0007] The wire disclosed in this specification is made of tungsten or a tungsten alloy. The tungsten wire has a tensile strength of 4600 MPa or more, and a 0.2% yield strength ratio for the tensile strength of 80.0% or more. Effect of the Invention

[0008] The tungsten wire disclosed in this specification can be used to produce a variety of products with excellent mechanical properties. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a cross-sectional perspective view showing a portion of a tungsten wire according to one embodiment. [Diagram 2] FIG. 2 is a flow chart showing an example of a method for manufacturing the tungsten wire of FIG. [Diagram 3] FIG. 3 is a cross-sectional perspective view showing a portion of an unfinished wire for the tungsten wire of FIG. [Figure 4] FIG. 4 is a cross-sectional view showing a schematic diagram of a die for the tungsten wire of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, preferred embodiments will be described in detail with reference to the drawings as appropriate.

[0011] The tungsten wire 2 shown in FIG. 1 is a single wire. The material of this tungsten wire 2 is tungsten or a tungsten alloy. The tungsten alloy contains tungsten as a main component and other elements. An example of the other elements is rhenium. The tungsten content in the tungsten alloy is preferably 50 mass% or more.

[0012] Various products can be obtained by subjecting this tungsten wire 2 to processing such as plastic processing, cutting, and heat treatment. Examples of the products include a reinforcing layer of a catheter, a probe pin, and a saw wire.

[0013] In FIG. 1, the arrow Dw is the diameter of the tungsten wire 2. Preferably, the diameter Dw is 0.10 mm or less. A minute product can be obtained from this tungsten wire 2. The diameter Dw is more preferably 0.07 mm or less, and particularly preferably 0.05 mm or less. The diameter Dw is preferably 0.01 mm or more.

[0014] Fig. 2 is a flow chart showing an example of a method for manufacturing the tungsten wire 2 of Fig. 1. In this manufacturing method, a basic wire is first prepared (STEP 1). This basic wire can be obtained through processes such as melting and solidifying a raw material to produce an ingot, and plastic processing of the ingot.

[0015] This raw wire is subjected to intermediate heat treatment (STEP 2). In the intermediate heat treatment, the raw wire is heated and slowly cooled. The preferred heating temperature in the intermediate heat treatment is 900°C or higher and 1100°C or lower. The preferred heating time in the intermediate heat treatment is 30 seconds or longer. The intermediate heat treatment improves the workability of the raw wire. The intermediate heat treatment is performed in an argon gas atmosphere or a hydrogen gas atmosphere.

[0016] This original wire is subjected to intermediate drawing (STEP 3). Multi-stage dies are used for intermediate drawing. The original wire passes through a first stage die, and then through multiple dies from the second stage onwards. The inner diameter of each die from the second stage onwards is smaller than the inner diameter of the die located upstream of this die. Intermediate drawing can be performed warm (600°C to 1000°C). Dry drawing using carbide dies or diamond dies can be employed. Through intermediate drawing, the original wire is made thinner and longer.

[0017] This intermediate heat treatment (STEP 2) and intermediate wire drawing (STEP 3) are repeated a predetermined number of times. By repeating this process, the raw wire is gradually thinned in diameter and gradually lengthened. By repeating this process, an unfinished wire is obtained (STEP 4).

[0018] Fig. 3 is a cross-sectional perspective view showing a part of the unfinished wire 4. In Fig. 3, an arrow Du indicates the diameter of the unfinished wire 4. This diameter Du is larger than the diameter Dw (see Fig. 1) of the tungsten wire 2. The material of the unfinished wire 4 is the above-mentioned tungsten or tungsten alloy.

[0019] The unfinished wire 4 is subjected to a final heat treatment (STEP 5). In the final heat treatment, the unfinished wire 4 is heated and slowly cooled. The preferred heating temperature in the final heat treatment is 600°C or higher and 800°C or lower. The preferred heating time in the final heat treatment is 10 seconds or higher and 30 seconds or lower. In the final heat treatment, the heating temperature is low and the heating time is short. Therefore, the amount of thermal energy given to the unfinished wire 4 by the final heat treatment is small. This final heat treatment can contribute to the characteristics of the tungsten wire 2 (described in detail later). The residual stress of the unfinished wire 4 is removed by the final heat treatment. In other words, the preferred final heat treatment is stress relief annealing. Preferably, the final heat treatment is performed in an argon gas atmosphere or a hydrogen gas atmosphere.

[0020] The unfinished wire 4 is heated (STEP 6). This heating is achieved by passing the traveling unfinished wire 4 through a burner or the like. The heating may also be achieved by passing the unfinished wire 4 through a cylindrical furnace. The heating conditions will be described in detail later. By heating, the unfinished wire 4 reaches a temperature higher than room temperature (23°C).

[0021] Following this heating (STEP 6), the finished wire is subjected to final drawing (STEP 7). Multi-stage dies may be used for the final drawing. The unfinished wire 4 passes through a first stage die, and then through multiple dies from the second stage onwards. The inner diameter of each die from the second stage onwards is smaller than the inner diameter of the die located upstream of this die. The final drawing reduces the diameter of the unfinished wire 4 and lengthens it. Between the die and the die downstream of this die, the unfinished wire 4 may be subjected to a heat treatment by a heating device. Heating (STEP 6) and final drawing (STEP 7) may be repeated.

[0022] In Fig. 4, the die 6 is shown together with the unfinished wire 4. The die 6 has an inlet 8 and an outlet 10. The unfinished wire 4 advances in a direction indicated by an arrow A1 in Fig. 4. In Fig. 4, the arrow Di indicates the diameter of the unfinished wire 4 before passing through the die 6, and the arrow Do indicates the diameter of the unfinished wire 4 after passing through the die 6. In the present invention, the area reduction rate R1 in the die 6 is calculated based on the following formula. R1 = (1 - (Do / Di) 2 )* 100 The area reduction rate R1 is preferably 10% or more and 22% or less. The area reduction rate R1 can contribute to the characteristics of the tungsten wire 2 (described in detail later). The area reduction rate R1 is more preferably 13% or more, and particularly preferably 15% or more. The area reduction rate R1 is particularly preferably 20% or less. In each die 6 used in the final wire drawing (STEP 7), the area reduction rate R1 is preferably within the above range.

[0023] In FIG. 4, the arrow α indicates the approach angle of the die 6. The approach angle α is preferably 4° or more and 8° or less. This approach angle α can contribute to the characteristics of the tungsten wire 2 (described in detail later). The approach angle α is more preferably 5° or more, and particularly preferably 6° or more. In each die 6 used in the final wiredrawing (STEP 7), the approach angle α is preferably within the above range.

[0024] In the final wire drawing (STEP 7), the die 6 through which the unfinished wire 4 passes last may have an approach angle α of 8° or more and 10° or less. This approach angle α can contribute to stabilizing the curl of the tungsten wire 2. The tungsten wire 2 with a stable curl is particularly suitable for saw wire.

[0025] The tensile strength TS of the tungsten wire 2 is preferably 4600 MPa or more. A catheter using this tungsten wire 2 as a reinforcing layer is less likely to buckle inside a patient's body. A probe pin obtained from this tungsten wire 2 has excellent spring properties. A saw wire using this tungsten wire 2 is less likely to break. This saw wire is suitable for semiconductor wafer manufacturing equipment. Furthermore, various products with excellent strength can be obtained from this tungsten wire 2. From these points of view, the tensile strength TS of the tungsten wire 2 is more preferably 5000 MPa or more, and particularly preferably 5300 MPa or more. The larger the tensile strength TS, the more preferable it is.

[0026] The 0.2% yield strength PS of the tungsten wire 2 is preferably 3680 MPa or more. A product obtained from this tungsten wire 2 can achieve a large elastic modulus. From this viewpoint, the yield strength PS is more preferably 3850 MPa or more, and particularly preferably 4000 MPa or more. The larger the 0.2% yield strength PS, the more preferable it is. The 0.2% yield strength PS is the stress at the point where 0.2% plastic strain occurs in the stress-strain curve. The 0.2% yield strength PS is derived by the offset method.

[0027] From the viewpoint of elastic modulus, the ratio of 0.2% proof stress PS to tensile strength TS (PS / TS) is preferably 80.0% or more, more preferably 80.5% or more, and particularly preferably 81.0% or more. Tungsten wire 2 having a large ratio (PS / TS) is particularly suitable for the reinforcing layer of a catheter. Tungsten wire 2 having a large ratio (PS / TS) is also particularly suitable for probe pins and other spring products.

[0028] The breaking elongation FE of the tungsten wire 2 is preferably 2.0% or more. This tungsten wire 2 can be subjected to high-degree plastic processing. From this viewpoint, the breaking elongation FE is more preferably 3.0% or more, and particularly preferably 3.4% or more. The tungsten wire 2 having a large breaking elongation FE is particularly suitable for probe pins and other spring products. The tungsten wire 2 having a large breaking elongation FE is also particularly suitable for saw wire.

[0029] The tensile strength TS, 0.2% proof stress PS, and breaking elongation FE are measured in accordance with the provisions of "JIS Z 2241". An example of a suitable device for the measurement is the tensile material tester "5565" manufactured by INSTRON. The measurement conditions are as follows. Gauge length: 100mm Tensile speed: 10mm / min Environmental temperature: 23℃

[0030] In the present invention, the area reduction rate R2 of the final wire drawing (STEP 7) is calculated based on the following formula. R2 = (1 - (Dw / Du) 2 )* 100 In this embodiment, the area reduction rate R2 is 95.0% or more. In other words, the final wire drawing (STEP 7) is a plastic processing with a high degree of processing.

[0031] The final wire drawing with a large area reduction rate R2 imparts toughness to the tungsten wire 2. This tungsten wire 2 has both the following characteristics (1) and (2). (1) The tensile strength TS is 4,600 MPa or more. (2) The ratio of proof stress PS to tensile strength TS (PS / TS) is 80.0% or more. The tungsten wire 2 may further have the following characteristic (3). (3) The 0.2% yield strength (PS) is 3680 MPa or more. From the viewpoint of toughness of the tungsten wire 2, the area reduction rate R2 is preferably 98.0% or more, and particularly preferably 99.0% or more.

[0032] The heating temperature in the heating step (STEP 6) is preferably 500°C or less. In other words, the temperature of the finishing wire in the final wire drawing (STEP 7) is relatively low. This final wire drawing can contribute to a large tensile strength TS of the tungsten wire 2. This final wire drawing can further contribute to a large ratio (PS / TS) of the tungsten wire 2. From these viewpoints, the heating temperature is more preferably 400°C or less, and particularly preferably 350°C or less. From the viewpoint of processability, the heating temperature is preferably 250°C or more.

[0033] The unfinished wire 4 that has been subjected to the final heat treatment (STEP 5) may be subjected to the final wiredrawing (STEP 7) without being subjected to the heating (STEP 6). In other words, the final wiredrawing (STEP 7) may be started in a cold state. This final wiredrawing can achieve a large tensile strength TS and a large ratio (PS / TS) of the tungsten wire 2. From the viewpoint of productivity of the final wiredrawing (STEP 7), it is preferable that the unfinished wire 4 that has been subjected to the heating step (STEP 6) is subjected to the final wiredrawing (STEP 7).

[0034] The tungsten wire 2 after the final wire drawing (STEP 7) may be subjected to a surface treatment. This surface treatment can remove oxides from the surface of the tungsten wire 2. A specific example of the surface treatment is electrolytic polishing. EXAMPLES

[0035] The effects of the tungsten wire according to the embodiment will be explained below, but the scope of the present specification should not be interpreted as being limited based on the description of the embodiment.

[0036] [Example 1] An original wire made of tungsten was prepared. The original wire was repeatedly subjected to intermediate heat treatment and warm wire drawing to obtain an unfinished wire having a diameter Du of 0.30 mm. The wire was subjected to a final heat treatment of 700°C. The unfinished wire was heated to 300°. The unfinished wire was subjected to final wire drawing using multiple dies. The approach angle α of each die was 6°. The area reduction rate R1 in each die was 15% to 20%. This final wire drawing produced a tungsten wire having a diameter Dw of 0.03 mm. The area reduction rate R2 of the final wire drawing was 99%. The tensile strength TS of this spring wire was 5026 MPa, the 0.2% proof stress PS was 4071 MPa, and the fracture elongation FE was 3.5%.

[0037] [Example 2] A tungsten wire of Example 2 was obtained in the same manner as in Example 1, except that the unfinished wire was not heated prior to the final wiredrawing.

[0038] [Comparative Example 1] The tungsten wire of Comparative Example 1 was obtained in the same manner as in Example 1, except that the heating temperature of the unfinished wire prior to the final drawing was set to 800°C, the approach angle α of each die was set to 12°, and the area reduction rate R1 of each die was set to 10% to 12%.

[0039] [Comparative Example 2] A tungsten wire of Comparative Example 2 was obtained in the same manner as in Example 1, except that the heating temperature of the unfinished wire prior to the final wiredrawing was set to 1000°C.

[0040] [Comparative Example 3] A tungsten wire of Comparative Example 3 was obtained in the same manner as in Example 1, except that the approach angle α of each die was set to 12°, resulting in a reduction in area rate R2 of 90%.

[0041] [Evaluation of buckling resistance] The vicinity of one end of the tungsten wire was extended horizontally, and the vicinity of this end was held in a cantilever. The length of the free portion of this wire (not held) was 33 mm. The vicinity of the other end of the wire sagged under its own weight. The vertical distance that the other end sagged was measured. The results are shown in Table 1 below as an index. Tungsten wires with less sagging are less likely to buckle when used as reinforcing wires for catheters, etc.

[0042] [Table 1]

[0043] As is clear from Table 1, the tungsten wires of the respective examples achieved excellent characteristic values. From these evaluation results, the superiority of these tungsten wires is clear.

[0044] [Disclosure items] Each of the following sections discloses a preferred embodiment.

[0045] [Item 1] The material is tungsten or a tungsten alloy. The tensile strength is 4600 MPa or more, The ratio of 0.2% yield strength to the tensile strength is 80.0% or more.

[0046] [Item 2] 2. The tungsten wire according to item 1, wherein the 0.2% proof stress is 3680 MPa or more.

[0047] [Item 3] 3. The tungsten wire according to item 1 or 2, having an elongation at break of 2.0% or more.

[0048] [Item 4] 4. The tungsten wire according to any one of items 1 to 3, having a diameter of 0.10 mm or less.

[0049] [Item 5] providing an unfinished wire; heating the unfinished wire to a temperature between room temperature and 500°C; and A process of performing final wire drawing on the unfinished wire using a die having an approach angle of 4° to 8° with an area reduction of 95.0% or more. A method for producing a tungsten wire comprising the steps of:

[0050] [Item 6] providing an unfinished wire; and A process of performing a final drawing on the unfinished wire by cold drawing using a die having an approach angle of 4° to 8° with an area reduction of 95.0% or more. A method for producing a tungsten wire comprising the steps of:

[0051] [Item 7] The reinforcing layer is formed by weaving a plurality of wires. The wire is made of tungsten or a tungsten alloy. The tensile strength of the wire is 4600 MPa or more, A catheter in which the ratio of the 0.2% yield strength of the wire to the tensile strength is 80.0% or more.

[0052] [Item 8] Equipped with a probe pin, The material of the probe pin is tungsten or a tungsten alloy, The tensile strength of the probe pin is 4600 MPa or more, A contact probe, in which the ratio of the 0.2% proof stress of the probe pin to the tensile strength is 80.0% or more.

[0053] [Item 9] Equipped with saw wire, The saw wire is made of tungsten or a tungsten alloy, The saw wire has a tensile strength of 4600 MPa or more, A wire saw device, wherein a ratio of 0.2% proof stress of the saw wire to the tensile strength is 80.0% or more. [Industrial Applicability]

[0054] The tungsten wire described above can be used as a material for various products that require excellent mechanical properties. [Explanation of symbols]

[0055] 2. Tungsten wire 4. Unfinished wire 6. Die 8...Entrance 10...exit

Claims

1. The material is tungsten or a tungsten alloy. The tensile strength is 4600 MPa or more, The tungsten wire has a ratio of 0.2% proof stress to tensile strength of 80.0% or more.

2. The tungsten wire according to claim 1, wherein the 0.2% yield strength is 3680 MPa or more.

3. 3. The tungsten wire according to claim 1 or 2, having an elongation at break of 2.0% or more.

4. 3. The tungsten wire according to claim 1 or 2, having a diameter of 0.10 mm or less.

5. providing an unfinished wire; A step of heating the unfinished wire to a temperature of the unfinished wire between room temperature and 500° C. and a step of subjecting the unfinished wire to a final wire drawing with a die having an approach angle of 4° to 8° and a reduction in area of ​​95.0% or more; A method for producing a tungsten wire comprising the steps of:

6. providing an unfinished wire; and a step of subjecting the unfinished wire to a final cold drawing with a die having an approach angle of 4° to 8° and a reduction in area of ​​95.0% or more; A method for producing a tungsten wire comprising the steps of:

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