Tungsten wire

Abstract

To provide a tungsten wire excellent in tensile strength.SOLUTION: A tungsten wire has a wire diameter of 5-30 μm and a crystallite size of 10-200 nm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to tungsten wire. [Background technology]

[0002] Conventionally, a tungsten wire is disclosed in, for example, Japanese Patent Laid-Open No. 2018-1434 (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-1434 A Summary of the Invention [Problem to be solved by the invention]

[0004] There was a demand for tungsten wire with excellent tensile strength. [Means for solving the problem]

[0005] The tungsten wire has a diameter of 5 μm or more and 30 μm or less, and a crystallite size of 10 nm or more and 200 nm or less. DETAILED DESCRIPTION OF THE INVENTION

[0006] [Description of the embodiments of the present disclosure] First, embodiments of the present disclosure will be listed and described.

[0007] Patent Document 1 discloses a tungsten wire with a surface roughness Ra of 0.10 μm or less. It also discloses a tensile strength of 3700 MPa to 4200 MPa, a hanging length of 900 mm per 1000 mm, and a wire diameter of 22 μm or less. It also discloses the form of a screen mesh for screen printing made using the tungsten wire, and the form of tungsten fiber as an absorbent for adsorbing radioactive materials.

[0008] Ultra-fine tungsten wires have low tensile strength, which can lead to frequent breakage during use. The reason for this is that tungsten wires have become thinner in recent years for various applications. As the wire diameter becomes smaller, the tensile stress applied to the wire during manufacturing and use increases, but the wire does not have sufficient tensile strength, resulting in breakage.

[0009] The tungsten wire of the present disclosure has a wire diameter of 5 μm or more and 30 μm or less, and a crystallite size of 10 nm or more and 200 nm or less.

[0010] Preferably, the surface roughness Sa is 50 nm or less, as this range further improves the tensile strength.

[0011] Preferably, the material contains at least one element selected from the group consisting of Si, K, La, and Ce in an amount of 10 mass ppm to 3 mass %.

[0012] This improves the tensile strength of the tungsten wire. <Wire diameter> The diameter of the tungsten wire is 5 μm or more and 30 μm or less.

[0013] Wire diameters of less than 5 μm are difficult to manufacture. Wire diameters of more than 30 μm result in a small tensile stress on the wire, making strength a non-issue.

[0014] The cross-sectional shape of the tungsten wire is basically round, and the tungsten wire is applicable to fields requiring tensile strength, such as saw wire and wire cutter. <Crystallite size> The crystallite size of tungsten wire is between 10 nm and 200 nm. By keeping the crystallite size within this range for thin wire, favorable results can be obtained in heat treatment, sintering, and wire drawing, thereby improving the tensile strength of the tungsten wire.

[0015] Crystallite sizes less than 10 nm are difficult to manufacture, and crystallite sizes greater than 200 nm result in low tensile strength. <Surface roughness Sa> The surface roughness Sa of the tungsten wire is 50 nm or less.

[0016] If the surface roughness Sa is 50 nm or less, the number of notches that are the starting points for fracture is reduced, resulting in higher tensile strength. <Amount of impurities> The content of at least one element selected from the group consisting of Si, K, La2O3, and CeO2 contained in the tungsten wire is 10 mass ppm or more and 3 mass % or less.

[0017] Within this range, the tensile strength can be maintained.

[0018] The content of components other than tungsten in the tungsten wire is 3.5 mass % or less.

[0019] <Tensile strength> Tensile strength 4000N / mm 2 More than 4300N / mm is preferable. 2 More preferably, it is equal to or greater than this. <Manufacturing method> Tungsten wire can be manufactured according to the following method. (1) Raw materials Tungsten powder with an FSSS average particle size of 5.0 μm and a purity of 99.9% or higher can be used. The FSSS average particle size and purity of the tungsten powder can be changed as needed. (2) Adjusting the particle size of the powder Tungsten powder is pulverized in a ball mill and the pulverized powder is subjected to wet centrifugation. This allows for the production of tungsten powder with small particle size and crystallite size. The crystallite size of the powder may be controlled by factors other than the average particle size. (3) Mixture When adding impurities, the impurity can be mixed with tungsten powder in a mortar to obtain doped tungsten powder. Additives that supply K, La, Ce, and Si include KCl (potassium chloride), La2O3 (lanthanum oxide), CeO2 (cerium oxide), and SiO2 (silicon oxide). (4) Press 680 tons (6.7 x 10 6 N) Using a press, 2.5 kg of mixed powder was added and the pressure was 140 kg / cm 2 The pressed body is made with a pressure of 15×17×900 mm. (5) Sintering Using a direct sintering furnace that passes an electric current directly through the pressed body (compressed powder body), sintering is carried out at a current value of 1800A in a hydrogen atmosphere for 1 minute, thereby obtaining a sintered body. (6) Swage Using a swaging device, the sintered body is swaged while being heated with a burner. During the swaging process, the sintered body is annealed in a hydrogen atmosphere in a heat treatment furnace. This process allows for the production of a linear body. (7) Wire drawing processing Using a wire drawing machine, the wire can be heated with a burner and drawn with a wire diameter reduction of 10% per die drawing ((wire diameter before processing - wire diameter after processing) / wire diameter before processing) (the reduction in the final die drawing can be changed depending on the target wire diameter). (8) Electrolytic polishing Electrolytic polishing of tungsten wire is performed using an electrolytic device. The electrolyte used can be an aqueous solution of potassium hydroxide.

[0020] [Details of the embodiments of the present disclosure] Example 1 (1) Preparation of tungsten wire (1-1) Raw materials Tungsten powder with an average particle size of 5.0 μm and a purity of 99.9% or more was used. (1-2) Adjusting the particle size of the powder Some tungsten powders were not particle size adjusted, while others were. The tungsten powders were ground in a ball mill and then wet centrifuged. This resulted in tungsten powders with hydrodynamic mean particle sizes (JIS Z 8828:2019) of 50, 100, 200, and 500 nm, as determined by dynamic light scattering. The average particle size of the tungsten powder was reduced by increasing the number of cycles, with grinding and centrifugation considered as one cycle. The crystallite sizes of the tungsten powders were 13, 30, 96, 189, and 523 nm. These crystallite sizes were determined from the Willamson-Hall plots obtained by 2θ-θ scanning of the powders using an X-ray diffractometer. (1-3) Press 680 tons (6.7 x 10 6 N) Using a press, 2.5 kg of mixed powder was added and the pressure was 140 kg / cm 2 The dimensions of the pressed body are 15 x 17 x 900 mm. (1-4) Sintering Using a direct sintering furnace in which an electric current is directly applied to the pressed body (green compact) for sintering, sintering was carried out at a current value of 1800 A in a hydrogen atmosphere for 1 minute, thereby obtaining a sintered body.

[0021] The purity of the sintered body was evaluated according to JIS H1403:2003. The elements included K, La, Ce, and Si, as well as Al, Ca, Cr, Cu, Fe, Mg, Mn, Ni, Pb, Sn, Na, O, C, and N as unavoidable impurity elements. K and Na were analyzed by atomic absorption spectrometry (Analytiquena contAA300), N and O by inert gas fusion / infrared absorption and thermal conductivity methods (LECO ON386), and other elements by ICP optical emission spectrometry (Shimadzu ICPS-8100CL). Purity is defined as the total mass minus the analyzed impurities divided by the total mass. In Example 1, the purity of the pure W sintered body was 99.9%. It was 2% by mass or more. (1-5) Swage Using a swaging device, the sintered body was swaged with a burner until it became φ3.7 mm. During the swaging process, it was annealed in a hydrogen atmosphere in a heat treatment furnace. This gave a linear body. (1-6) Wire drawing processing Using a wire drawing machine, the wire was heated with a burner and drawn to wire diameters of 35 μm, 15 μm, and 10 μm, with a wire diameter reduction per die drawing ((wire diameter before processing - wire diameter after processing) / wire diameter before processing) of 10% (the reduction in the final die drawing was changed depending on the target wire diameter). (1-7) Electrolytic polishing Tungsten wires were electrolytically polished using an electrolytic device. The finishing wire diameters were 30 μm, 10 μm, and 5 μm. A 24 vol% potassium hydroxide aqueous solution was used as the electrolyte. The voltage was adjusted based on the wire diameter. The feed speeds were 35, 50, 65, and 80 m / min. The surface roughness Sa was adjusted by the feed speed. This resulted in tungsten wires with sample numbers 1 to 15 shown in Table 1.

[0022] [Table 1]

[0023] (2) Evaluation of tungsten wire (2-1) Measurement of crystallite size Crystallite size was measured using X-ray diffraction. Measurements were performed at the hard X-ray beamline BL16 (Sumitomo Electric Industries Beamline) of the SAGA-LS synchrotron radiation facility. The X-ray wavelength was 0.0688 nm (18.009 keV). A Si111 monochromator was used, and a Pt (2.5 mrad) high-frequency light-removal mirror was used. The entrance slit size was 0.5 nm × 0.5 nm. The detector was a two-dimensional PILATUS100K detector with a camera length of 0.510 m. Diffracted light from a tungsten beam was measured in a configuration that measured the crystal plane spacing parallel to the drawing direction of the sample. The resulting two-dimensional profile was converted to data obtained by 2θ-θ scanning with a CuKα source (wavelength 0.15418 nm). The crystallite size was calculated by a Willamson-Hall plot of this data.

[0024] It is also possible to measure the crystallite size using a standard X-ray diffraction device by measuring with a bundle of tungsten wires. (2-2) Wire diameter measurement Measurement was performed using interference fringe laser diffraction measurement (CERSA-MCI LDS0200). (2-3) Surface roughness measurement The surface roughness Sa of the tungsten wire was measured using an atomic force microscope (Bruker Dimension Icon) in a measurement range of 3 μm × 3 μm. (2-4) Evaluation of tensile strength The tensile strength of the tungsten wire was measured using a tensile testing machine (Shimadzu AGS-5NX) with a gauge length of 200 mm and a crosshead speed of 50 mm / min.

[0025] These results are shown in Table 2.

[0026] [Table 2]

[0027] In the "crystallite size of wire" column of Table 2, if it was between 10 nm and 200 nm it was rated "B", and if it was in any other range it was rated "C". In the "surface roughness Sa of wire" column, if it was between 5 nm and 50 nm it was rated "A", and if it was in any other range it was rated "B". This evaluation is the same for Tables 4 and 6.

[0028] Table 2 shows that the crystallite size of the wire can be changed by changing the presence or absence of a crushing process and the powder particle size after crushing (powder crystallite size). If the crystallite size of the tungsten wire is 200 nm or less, the tensile strength is 4000 N / mm 2 It can be seen that the above is satisfactory. Example 2 The particle size adjustment step was carried out and the electrolytic polishing rate was changed to obtain tungsten wires of sample numbers 16 to 24 in the table below.

[0029] [Table 3]

[0030] [Table 4]

[0031] From Tables 3 and 4, if the surface roughness Sa is 50 nm or less, the tensile strength is 4300 N / mm 2 From the above, it can be seen that this is more preferable. Example 3 The particle size adjustment process was performed, and the powder particle size and electrolytic polishing conditions were kept constant, but the composition was changed by adding impurities to obtain tungsten wires with sample numbers 25 to 32 in the table below. The sintered body with 3% by mass of impurity added had a tungsten purity of 96.50% by mass or more.

[0032] [Table 5]

[0033] [Table 6]

[0034] It can be seen that the tensile strength is good when the amount of Si added is 10 mass ppm or more and 300 mass ppm or less, the amount of K added is 10 mass ppm or more and 100 mass ppm or less, the amount of La2O3 added is 0.05 mass% or more and 3 mass% or less, and the amount of CeO2 added is 0.05 mass% or more and 3 mass% or less.

[0035] The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is defined by the claims rather than the above-described embodiments, and it is intended to include any modifications within the scope of the claims and meanings equivalent to the claims.

Claims

1. A tungsten wire having a wire diameter of 5 μm or more and 30 μm or less and a crystallite size of 10 nm or more and 200 nm or less.

2. 2. The tungsten wire according to claim 1, wherein the surface roughness is Sa 50 nm or less.

3. Si, K, La ２ O ３ and CeO ２ The tungsten wire according to claim 1 or 2, containing at least one selected from the group consisting of 10 ppm by mass or more and 3% by mass or less.

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