Tungsten Alloy Wire and Metal Products

The present invention relates to a tungsten alloy wire and metal products.

Patent Literature (PTL) 1 discloses a tungsten wire having a tensile strength of at least 3900 MPa.

[PTL 1] Japanese Unexamined Patent Application Publication No. 2022-001660

An object of the present invention is to provide a tungsten alloy wire that is excellent in flex resistance and metal products that include the tungsten alloy wire.

In accordance with an aspect of the present invention, a tungsten alloy wire is to be used in an environment in which the tungsten alloy wire at least once undergoes a thermal effect at a temperature of at least 1100 degrees Celsius, and the tungsten alloy wire includes rhenium with a content of at least 5 wt % and at most 26 wt %.

In accordance with another aspect of the present invention, a metal product includes the above-described tungsten alloy wire.

According to the present invention, it is possible to provide a tungsten alloy wire excellent in flex resistance and metal products including the tungsten alloy wire.

Hereinafter, a tungsten wire and a metal mesh according to embodiments of the present invention will be described in detail with referenced to the drawings. It should be noted that each of the embodiments described below shows a specific example of the present invention. As such, the numerical values, shapes, materials, structural components, the arrangement and connection of the structural components, steps, the processing order of the steps, and so on, shown in the following embodiments are mere examples, and therefore do not limit the present invention. Among the structural components in the embodiments described below, those not recited in the independent claims will be described as optional structural components.

In addition, each diagram is a schematic diagram and not necessarily strictly illustrated. Accordingly, for example, scale sizes, etc. are not necessarily exactly represented. In each of the diagrams, substantially the same structural components are assigned with the same reference signs, and redundant descriptions will be omitted or simplified.

In addition, a term representing a shape of a component, such as “cylindrical” or “circular”, and a numerical range are used in the present description. Such terms and range are each not representing only a strict meaning of the term or range, but implying that a substantially same range, e.g., a range that includes even a difference as small as few percentages, is connoted in the term or range.

First, a tungsten alloy wire according to the present embodiment will be described with reference to.is a schematic perspective view of tungsten alloy wireaccording to the present embodiment.

As illustrated in, tungsten alloy wireis wound around winding frameand stored. Winding framemay be referred to as a bobbin, reel, spool, drum, or the like in some instances. Tungsten alloy wirehas, for example, but not particularly limited to, a total length ranging from the order of meters (m), such as approximately 100 m, to the order of kilometers (km).

Tungsten alloy wireillustrated inis utilized in the manufacture of metal products.toare each a schematic perspective view illustrating an example of a metal product that includes tungsten alloy wireaccording to the present embodiment.

Rodillustrated inis an example of the metal product and includes tungsten alloy wire. Specifically, rodis tungsten alloy wirehaving a predetermined length. The length of rodis not limited to a particular length and can be made to have a length appropriate to the application of rod. Rodis used as portions of various metal products including tungsten alloy wireor intermediate workpieces of the metal products. However, the application of rodis not limited to a particular application. It should be noted that the rod may be referred to as a pin.

Electrodeillustrated inis an example of the metal product and includes tungsten alloy wire. Specifically, electrodeis tungsten alloy wirehaving a predetermined length, and the tip portion of tungsten alloy wireis processed to be thin. The shape of the tip of electrodeis, for example, but not limited to, a cone shape. The shape of the tip of electrodemay be a cone shape with a round tip or a truncated-cone shape, a pyramid or truncated-pyramid shape, or the like. Electrodeis used in, for example, electric discharge machining. However, the application of electrodeis not limited to a particular application.

Twisted wireillustrated inis an example of the metal product and includes a plurality of tungsten alloy wires. Specifically, twisted wireis a plied yarn manufactured by performing doubling and twisting processing on the plurality of tungsten alloy wireshaving a predetermined length. It should be noted that twisted wiremay be a covered yarn that includes tungsten alloy wireas a core yarn or a sheath yarn. One of the core yarn and the sheath yarn may be a metal wire other than tungsten alloy wireor may be a chemical fiber, a natural fiber, a recycled fiber, or the like. Furthermore, twisted wiresmay be bundled to be used as a rope, a cord, or the like. The application of twisted wireis not limited to a particular application.

It should be noted that the examples of the metal products including tungsten alloy wireare not limited to those illustrated into. For example, the metal products may be a saw wire, a mesh, a catheter, a fiber product, and the like. The metal products may include tungsten alloy wireand a member that is formed of a material other than a metal (e.g., a resin).

Tungsten alloy wireaccording to the present embodiment is used in an environment in which tungsten alloy wireat least once undergoes a thermal effect at a temperature of at least 1100 degrees Celsius. Specifically, tungsten alloy wireat least once undergoes the thermal effect during processing for manufacturing the metal product or when tungsten alloy wireis used as the metal product. A specific example of the thermal effect is, for example, but not particularly limited to, the case where tungsten alloy wireis welded to another metal member such as that of iron or the case where tungsten alloy wireis used as a discharge electrode.

Even after undergoing the thermal effect at a temperature of at least 1100 degrees Celsius, tungsten alloy wireis bend-resistant. That is, tungsten alloy wireis excellent in flex resistance. Even when tungsten alloy wireis bent with a predetermined curvature, a break, a surface delamination, or the like does not occur in tungsten alloy wire. It should be noted that 1100 degrees Celsius is an example of a temperature at which tungsten undergoes primary recrystallization.

In general, tungsten has the property of withstanding a high temperature. However, tungsten has a problem such that its grain boundaries are fragile, that is, cracking originating from its grain boundary is likely to occur. Specifically, when tungsten undergoes a thermal effect to the extent sizes of grains change (specifically, at least a temperature at which tungsten undergoes primary recrystallization (1100 degrees Celsius)), grains of tungsten grow to reduce grain boundaries, and additionally, oxygen enters the grain boundaries. As the grain boundaries are reduced, the amount of oxygen entering the grain boundaries relatively increases, which decreases the strength of tungsten. As a result, when folding, bending, or the like sets up a stress in tungsten after the thermal effect, cracking originating from its grain boundary is likely to occur, causing a deterioration in flex resistance.

In contrast, tungsten alloy wireaccording to the present embodiment contains tungsten and rhenium (Re), and tungsten and rhenium are alloyed, forming a solid solution. A rhenium content of tungsten alloy wireis, for example, at least 5 wt % and at most 26 wt %. Alternatively, the rhenium content of tungsten alloy wiremay be at least 6 wt %, at least 7 wt %, at least 8 wt %, at least 9 wt %, at least 10 wt %, at least 12 wt %, at least 15 wt %, or at least 20 wt %. In addition, the rhenium content of tungsten alloy wiremay be at most 25 wt %, at most 20 wt %, at most 15 wt %, at most 12 wt %, at most 10 wt %, at most 9 wt %, at most 8 wt %, at most 7 wt %, or at most 6 wt %.

In tungsten alloy wire, when the rhenium content is at least 5 wt %, rhenium present in the grains can capture the oxygen entering when tungsten alloy wireundergoes the thermal effect. In this manner, the amount of oxygen present in the grain boundaries can be reduced, which makes the cracking unlikely to occur, and it is possible to restrain the deterioration in flex resistance.

Furthermore, in tungsten alloy wire, when the rhenium content is at most 26 wt %, the solid solution of rhenium and tungsten can be formed. A rhenium content exceeding 26 wt % fails to form the solid solution, and tungsten alloy wiremay decrease in strength to become brittle.

Next, the flex resistance of tungsten alloy wireaccording to the present embodiment will be described with reference toand.

is a table showing the flex resistances of tungsten alloy wires according to the present embodiment after undergoing the thermal effect. Working examples 1 to 8 shown inare tungsten alloy wires that differ from one another in at least one of diameter and composition. The diameters of tungsten alloy wiresaccording to the working examples are within the range of at least 0.02 mm and at most 1.00 mm. The rhenium contents of tungsten alloy wiresaccording to the working examples are within the range of at least 5 wt % and at most 26 wt %. Tungsten contents of tungsten alloy wiresaccording to the working examples are at least 74 wt % and at most 95 wt %.

also shows the flex resistances of tungsten wires according to comparative examples 1 to 7. Comparative examples 1 to 3 are tungsten alloy wires containing rhenium. The rhenium contents of the tungsten alloy wires according to the comparative examples 1 to 3 are 1 wt % or at most 3 wt %. The diameters of the tungsten alloy wires according to the comparative examples 1 to 3 are 0.10 mm or 0.50 mm. Comparative examples 4 to 6 are tungsten wires containing potassium (potassium-doped tungsten wires). The potassium contents of the potassium-doped tungsten wires according to the comparative examples 4 to 6 are 0.007 wt %. The diameters of the potassium-doped tungsten wires according to the comparative examples 4 to 6 are 0.04 mm, 0.10 mm, or 0.50 mm. A comparative example 7 is a pure tungsten wire, containing no additive. It should be noted that, in each of the working examples and comparative examples, trace amounts of inevitable impurities, which are inevitably mixed in the manufacture.

The inventors of the present invention performed heat treatment at predetermined temperatures on the tungsten alloy wires according to the working examples 1 to 8 and the tungsten alloy wires, the potassium-doped tungsten wires, and the pure tungsten wire according to the comparative examples 1 to 7. For each of the working examples and comparative examples, five samples were prepared, and the samples were subjected to the heat treatment at different temperatures (1100 degrees Celsius, 1300 degrees Celsius, 1500 degrees Celsius, 1700 degrees Celsius, and 2000 degrees Celsius). The duration of the heat treatment has no particular effect. For example, the duration of the heat treatment is approximately one minute.

After the heat treatment, the samples in the working examples and comparative examples were subjected to a coiling test.is a diagram illustrating an overview of the coiling test on tungsten alloy wireaccording to the present embodiment.

In the coiling test, tungsten alloy wirewas wound around core materialthat was rod-shaped, had a circular cross-sectional shape, and was uniform in diameter, and whether a break or a surface delamination occurred in tungsten alloy wirewas checked. Diameter R of a cross section of core materialused in the coiling test was made the same as diameter ϕ of tungsten alloy wireto be tested. That is, the coiling test is configured such that bending (coiling) is performed with a smaller radius of curvature (a larger curvature) for tungsten alloy wirehaving a smaller diameter. For example, in the case of tungsten alloy wireaccording to the working example 1, having a diameter of 1.00 mm, core materialthat had a columnar shape and a diameter of 1.00 mm was used. In the case of tungsten alloy wireaccording to the working example 7, having a diameter of 0.04 mm, core materialthat had a columnar shape and a diameter of 0.04 mm was used. These hold true for the tungsten alloy wires, the potassium-doped tungsten wires, and the pure tungsten wire according to the comparative examples 1 to 7.

In tungsten alloy wiresaccording to the working examples 1 to 8 in, neither break nor surface delamination occurred at any of the temperatures (denoted as “OK” in the table). That is, within the range where the rhenium content was at least 5 wt % and at most 26 wt %, it is possible to produce tungsten alloy wiresthat are bend-resistant (excellent in flex resistance) even after undergoing the thermal effect at a temperature of at least 1100 degrees Celsius, irrespective of their diameters.

In contrast, the comparative examples 1 to 3 showed that a break or a surface delamination occurred (denoted as “NG” in the table) in all of the tungsten alloy wires having rhenium contents of 1 wt % or 3 wt % except for the tungsten alloy wire according to the comparative examples 3 that underwent the thermal effect at 1100 degrees Celsius. In the comparative example 3, the diameter was as small as 0.10 mm. Therefore, it is considered that, at the low temperature (1100 degrees Celsius), the amount of oxygen incorporated in grain boundaries was small, which did not cause a break.

In addition, the comparative examples 4 to 6 showed that a break or a surface delamination occurred in all of the potassium-doped tungsten wires except for the potassium-doped tungsten wires that had small diameters and were subjected to the heat treatment at low temperatures (1100 degrees Celsius in the comparative example 5 and 1100 degrees Celsius and 1300 degrees Celsius in the comparative example 6). It should be noted that, unlike rhenium, potassium is present at grain boundaries and has no effect of capturing oxygen.

The comparative example 7 showed that a break or a surface delamination occurred in the pure tungsten wire because the thermal effect causes oxygen to enter grain boundaries.

As described above, tungsten alloy wireaccording to the present embodiment is to be used in an environment in which the tungsten alloy wire at least once undergoes a thermal effect at a temperature of at least 1100 degrees Celsius, and the tungsten alloy wire includes rhenium with a content of at least 5 wt % and at most 26 wt %.

With this configuration, in tungsten alloy wire, when at least 5 wt % of rhenium is contained, rhenium can capture oxygen entering grain boundaries when tungsten alloy wireundergoes the thermal effect, and thus it is possible to restrain the occurrence of cracking originating a grain boundary. Therefore, even after tungsten alloy wireundergoes the thermal effect, a break or the like is unlikely to occur in tungsten alloy wire, and thus it is possible to produce tungsten alloy wirethat is excellent in flex resistance.

Furthermore, when the rhenium content is at most 26 wt %, the alloy (solid solution) of rhenium and tungsten can be formed, and thus it is possible to increase the strength of tungsten alloy wire.

The metal product according to the present embodiment includes tungsten alloy wire. For example, the metal product is rod, electrode, or twisted wire.

With this configuration, tungsten alloy wireis bend-resistant even after undergoing the thermal effect during manufacturing or using the metal product. Accordingly, it is possible to restrain the metal product from deteriorating in quality.

Tungsten alloy wireaccording to the present embodiment can be manufactured by, for example, the following method.

First, tungsten powders and rhenium powders are mixed together and subjected to press molding and sintering to be made into an ingot. By adjusting the mixing ratio between the tungsten powders and the rhenium powders, the rhenium content can be adjusted to at least 5 wt % and at most 26 wt %.

Next, a tungsten block made into the ingot is formed into a wire shape by performing swaging processing in which the tungsten block is forged and compressed from around to be extended. Then, drawing (wire drawing) using wire drawing dies is performed. The drawing is performed using a plurality of wire drawing dies having different bore diameters in descending order of bore diameter.

By adjusting the bore diameters of the wire drawing dies as appropriate, it is possible to manufacture tungsten alloy wireshaving diameters within the range of 0.02 mm to 1.00 mm as shown in. It should be noted that the drawing may involve heating at a predetermined temperature. Furthermore, after the drawing, tungsten alloy wiremay be subjected to surface treatment such as electrolytic polishing.

Although the tungsten alloy wire and metal products according to the present invention have been described thus far based on the above-described embodiments, the present invention is not limited to the above-described embodiments.

For example, the tungsten alloy wire may contain ruthenium (Ru) or cobalt (Co) instead of rhenium. For example, the tungsten alloy wire may have a tungsten content of 99.8 wt % and a ruthenium content of 0.2 wt % and contain trace amounts of impurities. The tungsten alloy wire was subjected to the heat treatment and then to the coiling test. As a result, no deterioration in the flex resistance of the tungsten alloy wire was observed in any of the cases where the heat treatment was performed at temperatures of 1100 degrees Celsius, 1300 degrees Celsius, 1500 degrees Celsius, 1700 degrees Celsius, and 2000 degrees Celsius.

It should be noted that the present invention also includes other forms in which various modifications apparent to those skilled in the art are applied to the embodiments or forms in which structural components and functions in the embodiments are arbitrarily combined within the scope of the present disclosure.