Rhenium-tungsten wire, medical needle, probe pin, thermo-couple, and electronic tube heater

Abstract

To provide an ReW wire which facilitates long-term storage by suppressing discoloration.SOLUTION: A rhenium-tungsten alloy wire according to an embodiment is a wire made of a rhenium-containing tungsten alloy, wherein a ratio W / Re of an atomic concentration (atm%) of tungsten (W) to an atomic concentration (atm%) of rhenium (Re) determined by XPS analysis is 2.5 or more in an arbitrary measurement area having a diameter of 50 μm as a unit area on a surface of the wire. A medical needle according to an embodiment uses a rhenium-tungsten alloy wire according to an embodiment.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The embodiments described below relate to a rhenium-tungsten alloy wire, a method for producing the same, and a medical needle. [Background technology]

[0002] Tungsten alloy (ReW) wire containing a certain amount of rhenium (Re) has improved electrical resistance and wear resistance compared to regular tungsten (W) wire. It also has improved tensile strength over a wide temperature range and ductility after recrystallization. For this reason, it is used in semiconductor inspection probe pins, heaters for electron tubes, filaments for vibration-resistant light bulbs, thermocouples, fluorescent display filaments, medical needles, etc.

[0003] After the surface mixture layer created during the manufacturing process is removed by electrolytic polishing or other methods, ReW wire has a silvery white finish with a metallic luster. However, as the storage period increases, the surface discolors, for example, to blue, yellow, or reddish purple. Discoloration can cause changes in the electrical resistance of probe pins. In display tube filaments, the oxide coating (electrodeposited surface treatment) that emits thermions becomes uneven. In medical needles, quality degradation and impurity can become an issue, with changes in friction in the discolored area and the risk of the discolored area falling off.

[0004] As a result, the discolored parts are unusable and require additional processing, such as re-electrolysis. Furthermore, additional processing changes the wire size, electrical resistance, and strength, making it unusable and reducing yield. For this reason, after the electrolysis process, the wire is thoroughly dried, and the wound wire spool is sealed and packaged under reduced pressure and stored away from the external environment. However, there is variation in the degree of discoloration among ReW wires stored in the same manner. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 4-308003 [Patent Document 2] Patent Publication No. 2021-95585 [Non-patent literature]

[0006] [Non-Patent Document 1] Saburo Nagakura and five others, "Iwanami Dictionary of Physics and Chemistry, 5th Edition," Iwanami Shoten, February 1998, p. 541 Summary of the Invention [Problem to be solved by the invention]

[0007] The problem to be solved by the present invention is to provide a ReW wire that can be easily stored for a long period of time by suppressing discoloration. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the rhenium-tungsten alloy wire of the embodiment is made of the tungsten alloy containing rhenium, and in any measurement area of ​​unit area of ​​50 μm diameter on the wire surface, the ratio W / Re of the atomic concentration (atm%) of tungsten (W) and the atomic concentration (atm%) of rhenium (Re) by XPS analysis is more than 2.5.The rhenium content of the rhenium-tungsten alloy wire is more than 2wt% and less than 30wt%. [Brief explanation of the drawings]

[0009] [Figure 1] Figure 1 shows an example of the results of X-ray photoelectron spectroscopy (XPS) analysis of a discolored sample and a non-discolored sample. [Figure 2] FIG. 2 is a graph showing the discoloration of the ReW line and its reflectance spectrum. [Figure 3] FIG. 3 is a binary phase diagram of Re-W. [Figure 4a] Figure 4a shows the results of EDS (energy dispersive X-ray spectrometry) analysis of the cross section of the sample before removing the surface mixture layer. [Figure 4b] Figure 4b shows the results of EDS analysis of the cross section of the sample before removing the surface mixture layer. [Figure 4c] Figure 4c shows the results of EDS analysis of the cross section of the sample before removing the surface mixture layer. [Figure 5a] FIG. 5a is a potential-pH diagram for tungsten (W). [Figure 5b] FIG. 5b is a potential-pH diagram for rhenium (Re). [Figure 6] FIG. 6 is an explanatory diagram of particle size distribution. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, the rhenium-tungsten alloy wire of embodiment will be described with reference to drawings.Hereinafter, rhenium-tungsten alloy wire may be referred to as ReW wire.It should be noted that drawings are only schematic, and for example, the dimensional ratio of each part is not limited to drawings.

[0011] The rhenium-tungsten alloy wire of the embodiment is made of the tungsten alloy that contains rhenium, and in any measurement area of ​​unit area of ​​wire surface that is 50 μm in diameter, the ratio W / Re of tungsten (W) atomic concentration (atm%) and rhenium (Re) atomic concentration (atm%) by XPS analysis is more than 2.5.

[0012] Among rhenium oxides, Re2O5, also known as rhenium pentoxide, is a blue compound. ReO3, also known as rhenium trioxide, is a red cubic crystal with a metallic luster. Re2O7, also known as rhenium heptoxide, is a yellow orthorhombic crystal (Non-Patent Document 1). As such, rhenium oxides have color, and the color changes depending on the type of oxide. As a result of extensive research, it was discovered that rhenium oxide is responsible for the discoloration of ReW wire.

[0013] Figure 1 shows an example of the results of X-ray photoelectron spectroscopy (XPS) analysis of a discolored sample (A) and an undiscolored sample (B) using 26 wt% Re-W rays with a diameter of 0.152 mm, which had been electrolytically polished to a metallic luster and then stored for a certain period of time. The equipment used was a PHI Quantera SXM, with a single crystal spectrometer A1Kα ray source, an X-ray output of 12.5 W, and an analysis range of φ50 μm.

[0014] In sample B (non-tarnished), W-metal and tungsten oxide were detected in greater amounts than in sample A (tarnished), and in sample A, rhenium oxide was detected in greater amounts than in sample B. Table 1 shows the results of semi-quantitative XPS analysis of the same area, showing the ratio of tungsten (W) to rhenium (Re) atomic concentrations (W / Re). The tarnished sample has a higher rhenium content, which facilitates the formation of rhenium oxide. Table 1a shows the composition of the measured ranges of sample A (tarnished) and sample B (non-tarnished). Table 1a indicates that the surface of the ReW wire consists of C, N, O, W, and Re. Therefore, it can be said that the surface of the ReW wire may contain C, N, O, W, and Re. The C, N, and O contents of sample B (non-tarnished) are approximately equal to those of sample A (tarnished). Furthermore, the W content in the non-discolored sample (B) is greater than that in the discolored sample (A), and the Re content in the non-discolored sample (B) is less than that in the discolored sample (A).

[0015] [Table 1]

[0016] [Table 1a]

[0017] Figure 2 shows the discoloration of the ReW line and its reflectance spectrum. The discoloration exhibits the colors of the rhenium oxide mentioned above (blue, purple (red-blue), yellow). The reflectance spectrum of each discolored area was measured using a microspectroscopic system (DF-1037, manufactured by Techno-Synergy Co., Ltd.), which incorporates a spectroscopic system into a microscope and is capable of spectroscopic measurement of very small spots, under the following conditions: a measurement spot of approximately φ10 μm, an exposure time of 10 ms, and 200 accumulations.

[0018] For visible light wavelengths of 400nm to 700nm, the difference between the maximum and minimum reflectance values ​​for a silvery white (metallic color) without discoloration was 5% or less. On the other hand, the reflectance of discolored areas changed, with the spectrum exhibiting peaks at wavelengths corresponding to each color that were 5% or more different from the minimum value. From this, discolored areas can be identified visually or by checking whether the difference between the maximum and minimum reflectance values ​​in the 400nm to 700nm wavelength range of the reflection spectrum exceeds 5%. Figure 2 shows the difference between the maximum and minimum reflectance values ​​of the reflection spectrum, which is used to identify discolored areas.

[0019] One of the reasons why the abundance ratio of rhenium (Re) on the surface is high is the variation in the material of the wire. Figure 3 shows the binary phase diagram of Re-W. For example, Re-W is usually manufactured using a powder metallurgy method in which tungsten (W) powder and rhenium (Re) powder are mixed, molded, and sintered.

[0020] Because sintering of Re-W proceeds through solid-state diffusion, depending on the particle size distribution of each powder, the powder mixing state, or the molding and sintering conditions, it may be impossible to diffuse and homogenize (solid-solve) rhenium into the tungsten matrix. As a result, a phase region with a locally high rhenium composition ratio (σ-phase segregation phase) is formed. The presence of this on the surface increases the rhenium abundance ratio at the surface.

[0021] Furthermore, if the surface removal treatment of the ReW wire after the wiredrawing process, such as electropolishing, is insufficient, an unstable layer of composition may remain on the ReW wire surface, resulting in a high rhenium content. Figures 4a, 4b, and 4c show the results of EDS (energy dispersive X-ray spectrometry) analysis of the sample cross section before the surface mixture layer was removed. Figure 4a shows a secondary electron image of the sample cross section obtained by EDS. The arrow in Figure 4a indicates the surface mixture layer. As shown in Figure 4a, the thickness of the surface mixture layer is not uniform and varies. Figure 4b shows an EDS image of the tungsten elemental mapping of the sample cross section. As shown in Figure 4b, there are areas in the surface mixture layer with low tungsten concentration (indicated by the arrow in Figure 4b). Figure 4c shows an EDS image of the Re elemental mapping of the sample cross section. As shown in Figure 4c, there are areas in the surface mixture layer with high rhenium concentration (indicated by the arrow in Figure 4c). As is clear from the above analysis results, there are areas in the surface mixture layer where the rhenium concentration is high. Furthermore, the thickness of the surface mixture layer varies depending on the location. If the amount of surface removal is insufficient, the surface mixture layer may remain locally, resulting in a high rhenium content.

[0022] Furthermore, when surface treatment is performed using electrolytic polishing, depending on the electrolysis conditions, tungsten may dissolve preferentially, potentially increasing the abundance ratio of rhenium. Figures 5a and 5b show potential-pH diagrams for tungsten (W) and rhenium (Re). Figure 5a is the potential-pH diagram for tungsten (W). Figure 5b is the potential-pH diagram for rhenium (Re). In Figures 5a and 5b, the horizontal axis represents pH and the vertical axis represents potential (V). Because tungsten dissolves more easily, for example, when the electrolysis rate is slow or the electrolysis potential is low, tungsten tends to dissolve preferentially. This may increase the abundance ratio of rhenium on the surface.

[0023] In this embodiment, the ReW beam is subjected to surface polishing and semi-quantitative analysis is performed by XPS analysis. Surface polishing may be performed by chemical polishing, such as electrolytic polishing. XPS analysis is performed using, for example, a PHI Quantera SXM X-ray source with a single crystal spectrometer A1Kα beam, an X-ray output of 12.5 W, and an analysis range of φ50 μm.

[0024] In the ReW wire of the embodiment, the ratio W / Re of the atomic concentration (atm%) of tungsten (W) to the atomic concentration (atm%) of rhenium (Re) is 2.5 or more in an arbitrary measurement area as determined by XPS analysis. By setting the ratio W / Re of the atomic concentrations of tungsten and rhenium on the surface to 2.5 or more, the generation of rhenium oxide can be suppressed. Furthermore, when the ReW wire of the embodiment is used as a raw material to manufacture probe pins or medical needles, discoloration is suppressed and production yield is improved. The value of the ratio W / Re can be adjusted by, for example, at least one of the particle size of the raw tungsten powder, the particle size of the raw rhenium powder, the sintering temperature during production, and the polishing rate of electropolishing, or a combination of several of these.

[0025] The rhenium content of the ReW wire of the embodiment is, for example, 2 wt% or more and less than 30 wt%. The rhenium content of the ReW wire of the embodiment is, for example, preferably, 10 wt% or more and 28 wt% or less. The rhenium content is a value analyzed by inductively coupled plasma-optical emission spectrometry (ICP-OES). Rhenium improves the elongation of tungsten at high temperatures and enhances its workability. It also increases strength through solid solution strengthening.

[0026] If the rhenium content is less than 2 wt%, the effect is insufficient. For example, if a ReW wire with a rhenium content of less than 2 wt% is used as a probe pin material, the finished probe pin will deform significantly with frequent use, resulting in poor contact and reduced semiconductor inspection accuracy. If the rhenium content exceeds 30 wt%, the rhenium content exceeds the solid solubility limit with tungsten, making it impossible to diffuse and homogenize (solid-solve) rhenium into the tungsten matrix. As a result, a phase region with a locally high rhenium composition ratio (σ-phase segregation phase) may occur, potentially reducing the W / Re ratio in some areas. If such areas appear on the surface, they are prone to discoloration.

[0027] When a probe pin or medical needle is manufactured using a ReW wire containing 2 wt% or more but less than 30 wt% of rhenium, discoloration can be suppressed, production yield can be improved, and the mechanical properties (strength and abrasion resistance) of the manufactured probe pin or medical needle can be ensured. The rhenium content is preferably, for example, 10 wt% or more but less than 28 wt%.

[0028] The ReW wire of the embodiment may contain potassium (K) as a dopant in an amount of 30 wtppm to 90 wtppm. The potassium content is a value obtained by analysis using inductively coupled plasma optical emission spectroscopy (ICP-OES). The inclusion of potassium improves tensile strength and creep strength at high temperatures through the doping effect. If the potassium content is less than 30 wtppm, the doping effect becomes insufficient. If the potassium content exceeds 90 wtppm, workability may decrease, resulting in a significant decrease in yield. By containing potassium as a dopant in an amount of 30 wtppm to 90 wtppm, for example, thin wires for thermocouples and electron tube heaters made from the ReW wire of the embodiment can be produced with high yield while maintaining high-temperature properties (preventing breakage and deformation during high-temperature use).

[0029] The ReW wire of the embodiment has a diameter of, for example, 0.1 mm or more and 1.00 mm or less.

[0030] The ReW wire of this embodiment is prevented from discoloring on the surface, which contributes greatly to long-term storage and improved yield. The ReW wire of this embodiment can also be used for medical needles, thermocouples, and probe pins.

[0031] Next, a method for manufacturing a ReW wire according to the embodiment will be described. The manufacturing method is not particularly limited, but the following method can be given as an example.

[0032] Tungsten powder and rhenium powder are mixed so that the rhenium content is 2 wt% or more but less than 30 wt%. While the mixing method is not particularly limited, a method in which the powders are slurried using water or an alcohol-based solution and mixed is particularly preferred, as this produces a powder with good dispersibility. Furthermore, to ensure the homogeneity of the powder lot, it is even more preferable to dry the slurry and then dry-mix the same powder lot together.

[0033] The rhenium powder to be mixed preferably has an average particle size of less than 8 μm. The particle size distribution preferably has an SD value of less than 11 μm. Figure 6 shows an explanatory diagram of particle size distribution. The horizontal axis represents particle size (μm), the left vertical axis represents frequency (%), and the right vertical axis represents cumulative (%). The SD value is calculated by SD = (d(84%) - d(16%)) / 2, where d(84%) is the cumulative 84% particle size and d(16%) is the cumulative 16% particle size. This value serves as a guide to the distribution width of the measured particle size. The particle size distribution is measured using a laser diffraction method. The amount of powder used per measurement should be the amount recommended for the measuring device. Generally, 0.02 g is recommended. The measurement sample should be thoroughly stirred before weighing.

[0034] The tungsten powder is either pure tungsten powder excluding unavoidable impurities, or doped tungsten powder containing potassium (K) in an amount that takes into account the yield of wire rod. The tungsten powder preferably has an average particle size of less than 16 μm. The particle size distribution preferably has an SD value of less than 13 μm.

[0035] When the average particle size of the rhenium powder is 8 μm or more, when the SD value of the rhenium powder is 11 μm or more, when the average particle size of the tungsten powder is 16 μm or more, or when the SD value of the tungsten powder is 13 μm or more, the diffusion distance of the rhenium atoms or tungsten atoms increases in order to diffuse and homogenize (solid-solve) the rhenium into the tungsten matrix, making it easier to generate the σ phase.

[0036] The ratio of the average particle size of the rhenium powder to the average particle size of the tungsten powder (average particle size of Re / average particle size of W) is preferably 0.4 or more and 2.0 or less. If the ratio of the average particle size of the rhenium powder to the average particle size of the tungsten powder is less than 0.4 or exceeds 2.0, the diffusion distance of the rhenium atoms to the center of the tungsten particle, or the diffusion distance of the tungsten atoms to the center of the rhenium particle, becomes long, and the σ phase may be easily generated.

[0037] Next, the mixed powder is placed in a predetermined mold and press-molded. The pressing pressure at this time is preferably 150 MPa or higher. To facilitate handling, the molded body may be pre-sintered at 1200 to 1400°C in a hydrogen furnace. The resulting molded body is sintered in a hydrogen atmosphere, an inert gas atmosphere such as argon, or a vacuum. The sintering temperature is preferably 2500°C or higher. If the sintering temperature is lower than 2500°C, the diffusion of rhenium atoms and tungsten atoms during sintering will not proceed sufficiently. The upper limit of the sintering temperature is 3400°C (below the melting point of tungsten, 3422°C).

[0038] The relative density of the sintered body (relative density to true density (%) = [sintered body density / true density] × 100%) is preferably 90% or more. Furthermore, the ratio of the density of the lowest part of a sintered body, for example, the bottom end in electric sintering, to the overall average density of the same sintered body is preferably 0.98 or more. By making the relative density of the sintered body 90% or more and the ratio of the density of the lowest part to the overall average density of the same sintered body 0.98 or more, fluctuations in the rhenium content can be suppressed.

[0039] The sintered body obtained in this sintering step is subjected to a first swaging (SW) process. The first swaging process is preferably carried out at a heating temperature of 1300 to 1600°C. The reduction rate of the cross-sectional area (area reduction rate) in one heat treatment (one heat) is preferably 5 to 15%.

[0040] Rolling may be performed instead of the first rolling and punching process. The rolling is preferably performed at a heating temperature of 1200 to 1600°C. The area reduction rate per heat is preferably 40 to 75%. As the rolling mill, a two-way roller rolling mill, a four-way roller rolling mill, a die roll rolling mill, or the like can be used. Rolling can significantly improve manufacturing efficiency. The first rolling and punching (SW) process may be combined with rolling.

[0041] The sintered body (ReW bar) that has been subjected to the first rolling, rolling, or a combination of the first rolling and rolling is subjected to the second rolling (SW) process. The second rolling is preferably performed at a heating temperature of 1200 to 1500°C. The area reduction rate per heating (one heat) is preferably about 5 to 20%.

[0042] The ReW bar that has undergone the second rolling process is then subjected to a recrystallization treatment, which can be carried out using, for example, a high-frequency heating device in a hydrogen atmosphere, an inert gas atmosphere such as argon, or a vacuum at a treatment temperature in the range of 1800 to 2600°C.

[0043] The ReW bar that has completed the recrystallization treatment is subjected to the third rolling and striking process. The third rolling and striking process is preferably carried out at a heating temperature of 1200 to 1500°C. The area reduction rate per heat is preferably about 10 to 30%. The third rolling and striking process is carried out until the ReW bar has a diameter that can be drawn (preferably 2 to 4 mm).

[0044] After the third rolling process, the ReW rod material is lubricated on the surface and then dried to enable smooth wire drawing (DW) processing. The wire drawing process involves repeatedly applying the lubricant, drying the lubricant, heating to a workable temperature, and drawing using a drawing die. It is preferable to use a carbon (C)-based lubricant, which has excellent heat resistance.

[0045] The processing temperature is set according to the wire diameter to be drawn. The processing temperature is preferably 1100°C or lower, for example. The area reduction rate per die is preferably 10 to 35%. During the wire drawing process, an annealing process or a surface polishing process (e.g., an electrolysis process) may be added under known conditions, as necessary.

[0046] The ReW wire that has completed the wire drawing process is polished. For example, the polishing process can be performed by electrochemical polishing (electrolytic polishing) in a sodium hydroxide solution with a concentration of 3 to 15 wt%. The area reduction rate in the polishing process is preferably 10 to 25%. If it is less than 10%, it may not be possible to remove the unevenness on the material surface that occurs during the rolling and wire drawing processes, and the mixture that adheres to the unevenness on the material surface. If the amount of surface removal is insufficient, a layer of the mixture may remain locally, which may increase the proportion of rhenium. If it exceeds 25%, the material yield will decrease.

[0047] In the case of electrolytic polishing, the polishing speed is preferably 0.5 to 3.0 μm / sec. If the polishing speed is slower than 0.5 μm / sec, the tungsten on the surface may be preferentially dissolved, increasing the proportion of rhenium on the surface. If the polishing speed exceeds 3.0 μm / sec, the amount of electrolysis per unit time increases, resulting in rapid electrolysis and possibly insufficient correction of the cross-sectional shape of the ReW wire.

[0048] After polishing, the ReW wire may be subjected to a drying process, for example. The drying process is carried out, for example, in a vacuum dryer with the temperature inside the dryer set to a range of 50 to 80°C. The drying time is, for example, one hour or more. After that, a predetermined shipping inspection is carried out. When storing the ReW wire after vacuum drying, it can be stored in a moisture-proof storage cabinet with a relative humidity of 5% or less to prevent moisture absorption. For example, except when conducting characteristic or quantity inspections, the ReW wire is stored in the moisture-proof storage cabinet.

[0049] The ReW wire is, for example, wound onto a shipping spool while undergoing a shipping inspection. After the shipping inspection, the outermost surface of the ReW wire wound onto the shipping spool is covered with protective paper and fixed with a rubber band, etc. Then, the wire is stored in, for example, an aluminum bag, degassed, and sealed.

[0050] By using an appropriate amount of the ReW wire obtained in the above-mentioned process and carrying out the necessary processes under known conditions, a probe pin or medical needle with a specified wire diameter and the required properties (strength, hardness, etc.) can be obtained.

[0051] Example 1 Doped tungsten powder with an average particle size of 13 μm and SD of 12 μm, containing potassium (K) in an amount that would result in a final wire of 50 wtppm to 80 wtppm, and rhenium powder with an average particle size of 6 μm and SD of 7 μm were mixed in an alcoholic solution to form a slurry with a rhenium content of 10 wt%. The resulting slurry was dried to form the raw material powder.

[0052] The mixed powder of raw materials was press-molded to obtain a green body. The green body was subjected to preliminary sintering treatment at 1300°C in a hydrogen furnace. The green body was then sintered at 3000°C in a hydrogen atmosphere to obtain a sintered body. The sintered body was subjected to a first rolling process at a heating temperature of 1400°C, with a cross-sectional area reduction rate of 14% per heat treatment. The sintered body that had undergone the first rolling process was subjected to a second rolling process at a heating temperature of 1300°C, with a cross-sectional area reduction rate of 15% per heat treatment.

[0053] After the second rolling process, the ReW rod was recrystallized in a hydrogen atmosphere at a temperature of 2400°C. After the recrystallization process, the third rolling process was carried out at a heating temperature of 1300°C, with a cross-sectional area reduction rate of 13% per heating process, to obtain a rod with a diameter of 2.5 mm.

[0054] A lubricant was applied to the surface of the bar material that had been subjected to the third rolling process, and the bar material was then dried. The obtained bar material was then subjected to wire drawing. The wire drawing was performed at 1000°C, with the cross-sectional area reduction rate per drawing being 10% to 35%. The wire drawing process was followed by an annealing step at 1300°C.

[0055] After the wire drawing process, the ReW wire was electropolished in an 8 wt% sodium hydroxide aqueous solution. The electropolishing process was carried out with a cross-sectional area reduction rate of 15-20% and a polishing rate of 2.2 μm / sec. The wire diameter of the obtained ReW wire was 0.8 mm.

[0056] After electropolishing, the ReW was dried for two hours in a vacuum dryer at a temperature of 70°C. The resulting ReW wire was wound onto a shipping spool of 100 m per spool, the outermost surface covered with protective paper, and secured with a rubber band. The shipping spool with the wound ReW wire was placed in an aluminum bag together with a desiccant containing silica gel, and the aluminum bag was degassed and sealed.

[0057] Three similar spools were manufactured, and the three spool samples were stored for eight months, lined up on a 1-meter-high stand in a room with a humidity of 60% or less and a room temperature of 30°C or less. After eight months, the presence or absence of discoloration was confirmed using the method described above (the difference between the maximum and minimum reflectance values ​​in the wavelength range of 400 nm to 700 nm in the reflectance spectrum, as explained with reference to Figure 2).

[0058] Example 2 A ReW wire was manufactured in the same manner as in Example 1, except that the raw tungsten powder was not doped with potassium, the rhenium content was 26 wt%, and the final ReW wire diameter was 0.15 mm. The wire was wound onto a shipping spool of 500 m per spool and stored in an aluminum bag together with a desiccant using the same packaging method as in Example 1. As in Example 1, three identical spools were manufactured and stored for eight months using the same method as in Example 1. After eight months, the presence or absence of discoloration was confirmed.

[0059] (Comparative Example 1) A ReW wire was manufactured using the same raw material powder as in Example 1, and the same processes as in Example 1 were carried out up to the wiredrawing process. The obtained ReW wire was subjected to an electrolytic polishing process at a polishing rate of 0.4 μm / sec to obtain a ReW wire with a wire diameter of 0.8 mm. The obtained ReW wire was wound on a shipping spool of 100 m per spool, the outermost surface was covered with protective paper, and the spool was secured with a rubber band. The shipping spool on which the ReW wire was wound was placed in an aluminum bag together with a desiccant containing silica gel, and the aluminum bag was degassed and sealed. Three identical spools were manufactured and stored for eight months using the same method as in Example 1. After eight months, the presence or absence of discoloration was confirmed.

[0060] (Comparative Example 2) A ReW wire was produced using the same raw material powder as in Example 2, and the same processes as in Example 2 were carried out up to the wiredrawing process. The obtained ReW wire was subjected to an electrolytic polishing process at a polishing speed of 0.4 μm / sec to obtain a ReW wire with a wire diameter of 0.15 mm. The obtained ReW wire was wound onto a shipping spool of 500 m per spool and packaged in the same manner as in Comparative Example 1. Three identical spools were produced and stored for eight months in the same manner as in Example 1. After eight months, the presence or absence of discoloration was confirmed.

[0061] Table 2 shows the measurement results for the rhenium content, potassium content, and W / Re. The rhenium content and potassium content were analyzed using inductively coupled plasma optical emission spectroscopy (ICP-OES). The lower detection limit for potassium is 5 wtppm, and values ​​below 5 wtppm without addition are indicated by "-". W / Re was determined by XPS analysis. XPS analysis was performed using a PHI Quantera SXM, with a single crystal spectrometer A1Kα ray source, an X-ray output of 12.5 W, and an analysis range of φ50 μm.

[0062] [Table 2]

[0063] As can be seen from Table 2, the ReW wires according to the embodiments can suppress discoloration even during long-term storage, and can significantly improve the yield in medical needle processing. In the ReW wires of Comparative Examples 1 and 2, the electrolytic polishing rate was slow, so the abundance ratio of rhenium on the surface increased, and the W / Re ratio was smaller than 2.5.

[0064] Although several embodiments of the present invention have been described above, these embodiments are presented by way of example only and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. Modifications of these embodiments are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims. Furthermore, the above-described embodiments can be implemented in combination with each other.

[0065] The following describes the invention in terms of embodiments.

[0066] <1> A tungsten rhenium alloy wire is a wire made of a tungsten alloy containing rhenium, and in an arbitrary measurement area on the wire surface with a unit area of ​​50 μm in diameter, the ratio W / Re of the atomic concentration (atm%) of tungsten (W) to the atomic concentration (atm%) of rhenium (Re) measured by XPS analysis is 2.5 or more. <2> The rhenium content is 2 wt% or more and less than 30 wt%; <1> The rhenium-tungsten alloy wire according to claim 1. <3> The rhenium content is 10 wt% or more and 28 wt% or less, <1> The rhenium-tungsten alloy wire according to claim 1. <4> The potassium (K) content is 30 wtppm or more and 90 wtppm or less. <1> Or <3> The tungsten rhenium alloy wire according to any one of claims 1 to 14. <5> The diameter is 0.1 mm or more and 1.00 mm or less, <1> Or <4> The tungsten rhenium alloy wire according to any one of claims 1 to 14. <6> Used as wire for medical needles, <1> Or <5> The rhenium-tungsten alloy wire according to any one of claims 1 to 10. <7> <1> Or <6> A method for producing the rhenium-tungsten alloy wire according to any one of claims 1 to 14. <8> <1> Or <6> A medical needle using the tungsten rhenium alloy wire according to any one of claims 1 to 4. [Explanation of symbols]

[0067] A: Discolored sample B: No discoloration sample

Claims

1. A wire made of a tungsten alloy containing rhenium, wherein the ratio W / Re of the atomic concentration (atm%) of tungsten (W) to the atomic concentration (atm%) of rhenium (Re) measured by XPS analysis in any measurement area of ​​a unit area of ​​50 μm diameter on the wire surface is 2.5 or more.

2. 2. The tungsten rhenium alloy wire according to claim 1, wherein the rhenium content is 2 wt% or more and less than 30 wt%.

3. 2. The tungsten rhenium alloy wire according to claim 1, wherein the rhenium content is 10 wt % or more and 28 wt % or less.

4. 2. The tungsten rhenium alloy wire according to claim 1, wherein the potassium (K) content is 30 wtppm or more and 90 wtppm or less.

5. 2. The tungsten rhenium alloy wire according to claim 1, wherein the diameter is 0.1 mm or more and 1.00 mm or less.

6. The tungsten rhenium alloy wire according to any one of claims 1 to 5, which is used as a wire material for medical needles.

7. 6. The method for producing a tungsten rhenium alloy wire according to claim 1.

8. A medical needle using the tungsten rhenium alloy wire according to any one of claims 1 to 5.

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