Tungsten wire

Abstract

This tungsten wire (1) contains tungsten as a main component. When the tensile strength of the tungsten wire (1) is set as T (unit: MPa) and the wire diameter is set as D (unit: mm), 4758 * D2-7258.3 * D + 5275.5 < = T < = 4758 * D2-7258.3 * D + 6100 is satisfied. The perfect roundness of the tungsten wire (1) is 2.0% or less.

Description

Technical Field

[0001] The present invention relates to tungsten wire. Background Art

[0002] Patent Document 1 discloses a tungsten wire having a tensile strength of 4800 MPa or more.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2020-105548 Summary of the invention

[0006] Problems to be solved by the invention

[0007] In the conventional tungsten wire, when the tensile strength increases and the amount of additives increases, the workability of wire drawing using a die deteriorates. Therefore, the die becomes easily worn, and the roundness of the tungsten wire deteriorates.

[0008] Therefore, an object of the present invention is to provide a tungsten wire having an optimized circularity.

[0009] Means for solving problems

[0010] The tungsten wire of one embodiment of the present invention contains tungsten as a main component. When the tensile strength is set to T (unit: MPa) and the wire diameter is set to D (unit: mm), 4758×D 2 -7258.3×D+5275.5≤T≤4758×D 2 -7258.3×D+6100. The circularity of the tungsten wire is 2.0% or less.

[0011] Effects of the Invention

[0012] According to the present invention, a tungsten wire having an optimized circularity can be realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram showing the appearance and cross section of a tungsten wire according to an embodiment.

[0014] Figure 2 This is a diagram for explaining the circularity.

[0015] Figure 3 This is a flowchart showing an example of a method for producing a tungsten wire according to an embodiment.

[0016] Figure 4 1 is a flowchart showing another example of the method for producing the tungsten wire according to the embodiment.

[0017] Figure 5This is a graph showing the relationship between the wire diameter and the tensile strength of a tungsten wire containing rhenium or cerium.

[0018] Figure 6 This is a graph showing the relationship between the rhenium content, tensile strength, and circularity of a tungsten wire having a wire diameter of 50 μm and containing rhenium.

[0019] Figure 7 This is a graph showing the relationship between the rhenium content, tensile strength, and circularity of a tungsten wire having a wire diameter of 30 μm and containing rhenium.

[0020] Figure 8 This is a graph showing the relationship between the cerium content, the tensile strength, and the circularity of a tungsten wire having a wire diameter of 30 μm and containing cerium. DETAILED DESCRIPTION

[0021] Hereinafter, the tungsten wire of the embodiment of the present invention will be described in detail using the accompanying drawings. It should be noted that the embodiments described below are all embodiments that represent a specific example of the present invention. Therefore, the numerical values, shapes, materials, components, configurations and connection forms of components, steps, and the order of steps shown in the following embodiments are examples, and the main purpose is not to limit the present invention. Therefore, among the components in the following embodiments, the components that are not described in the independent claims are described as optional components.

[0022] In addition, each figure is a schematic diagram and may not be illustrated strictly. Therefore, for example, the scales in each figure may not be consistent. In addition, in each figure, the same symbols are marked for substantially the same structure, and repeated descriptions are omitted or simplified.

[0023] In the present specification, terms indicating the relationship between elements, terms indicating the shape of an element, and numerical ranges are not intended to have strict meanings but are intended to include substantially equivalent ranges, for example, differences of about several %.

[0024] (Implementation Method)

[0025] [Tungsten Wire]

[0026] First, for the tungsten wire of the embodiment, use Figure 1 Provide explanation. Figure 1 It is a schematic diagram showing the appearance and cross section of the tungsten wire 1 according to the present embodiment.

[0027] like Figure 1 As shown in FIG. 1 , the tungsten wire 1 is stored by being wound around a reel 2. The reel 2 is sometimes referred to as a bobbin, a reel, a bobbin, a drum, etc. The tungsten wire 1 has a total length of the order of kilometers, for example, not less than 50 km and not more than 300 km.

[0028] Figure 1The tungsten wire 1 shown in is used in the manufacture of tungsten products. For example, the tungsten wire 1 is used as the core wire of a saw wire. Specifically, the saw wire is a wire of a fixed abrasive type, having a tungsten wire 1 as a core wire, and further having abrasive particles such as diamond particles or cubic boron nitride (CBN) particles. The abrasive particles are bonded to the surface of the tungsten wire 1. Bonding can be electrodeposition or bonding using resin bonding. In addition, the saw wire can also be a wire of a free abrasive type. For example, the saw wire can also be the tungsten wire 1 itself without abrasive particles.

[0029] Saw wires are used, for example, to cut semiconductor ingots such as silicon (Si) or silicon carbide (SiC). Semiconductor wafers can be manufactured by cutting semiconductor ingots using saw wires. At this time, the smaller the wire diameter of the saw wire, the smaller the amount of cutting becomes, so the loss is reduced and the number of wafers obtained can be increased. It should be noted that the cutting object is not limited to semiconductor ingots, but can also be glass, concrete, crystal or ceramics.

[0030] The tungsten wire 1 contains tungsten (W) as a main component. The "main component" means that the content (content rate) of the element is more than 50wt%. For example, the content of tungsten contained in the tungsten wire 1 is 97wt% or more. The content of tungsten contained in the tungsten wire 1 may be 99wt% or more, 99.9wt% or more, or 99.99wt% or more. In addition to the additives described below, the tungsten wire 1 may also contain inevitable impurities that are inevitably mixed in the manufacturing process.

[0031] The tungsten wire 1 contains, for example, rhenium (Re). The content of rhenium in the tungsten wire 1 is, for example, 0.1 wt % or more and 3 wt % or less. Rhenium and tungsten form an alloy (solid solution).

[0032] When the content of rhenium is high, the tensile strength of the tungsten wire 1 can be improved. On the other hand, when the content of rhenium is too high, it is difficult to thin the tungsten wire 1 while maintaining the tensile strength of the tungsten wire 1 at a high level. Specifically, wire breakage is likely to occur, and it becomes difficult to draw the wire in a long strip. By reducing the content of rhenium and setting the content of tungsten to 97 wt % or more, the processability of the tungsten wire 1 can be improved. In addition, by reducing the content of rare and expensive rhenium, it is possible to mass-produce inexpensive tungsten wire 1 in a long strip.

[0033] It should be noted that the metal used in the alloy with tungsten may also be osmium (Os), ruthenium (Ru) or iridium (Ir). The content of osmium, ruthenium or iridium is, for example, the same as the content of rhenium. These cases can also obtain the same effect as the case of rhenium tungsten alloy. In addition, the tungsten wire 1 may also be made of an alloy of tungsten and two or more metals other than tungsten.

[0034] The tungsten wire 1 may contain potassium (K). The content of potassium in the tungsten wire 1 is, for example, 0.001 wt% or more and 0.01 wt% or less. Potassium exists in the crystal grain boundaries of tungsten. Even the tungsten wire 1 containing potassium can achieve a tensile strength higher than the general tensile strength of piano wire.

[0035] In addition, the tungsten wire 1 may also contain rare earth elements. The content of rare earth elements in the tungsten wire 1 is, for example, greater than 0.03wt% and less than 0.3wt%. The content of rare earth elements in the tungsten wire 1 may also be, for example, greater than 0.03wt% and less than 0.09wt%. Rare earth elements are, for example, cerium (Ce), lanthanum (La), yttrium (Y), or samarium (Sm). Rare earth elements exist at the crystal grain boundaries of tungsten. Even the tungsten wire 1 containing rare earth elements can achieve a tensile strength higher than the general tensile strength of piano wire.

[0036] As an example, the wire diameter of the tungsten wire 1 is 100 μm or less. The smaller the wire diameter of the tungsten wire 1 becomes, the more the loss of the cut material can be reduced when it is used as the core wire of the saw wire. The wire diameter of the tungsten wire 1 may be 80 μm or less, 70 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, or 15 μm or less. In addition, if the manufacturing method described later is used, a tungsten wire 1 with an extremely fine wire diameter of 13 μm or less can also be achieved. The wire diameter of the tungsten wire 1 may be 10 μm or less, 8 μm or less, or 7 μm or less. The wire diameter of the tungsten wire 1 is, for example, 5 μm or more, but is not limited to this.

[0037] In addition, as an example, the tensile strength of the tungsten wire 1 is 4800 MPa or more. The tensile strength may be 4900 MPa or more, 5000 MPa or more, 5200 MPa or more, or 5500 MPa or more. In addition, a tungsten wire 1 having an extremely high tensile strength of 5800 MPa or more may be achieved. The tensile strength of the tungsten wire 1 may be 5900 MPa or more, or 6000 MPa or more. The tensile strength may be measured, for example, based on the tensile test of the Japanese Industrial Standard (JIS H44608).

[0038] The tungsten wire 1 of this embodiment satisfies the prescribed relationship when the tensile strength is set to T (unit: MPa) and the wire diameter is set to D (unit: mm). Specifically, a tungsten wire 1 having a higher tensile strength than the conventional one corresponding to the wire diameter is realized. The specific relationship between the tensile strength T and the wire diameter D is described together with the specific examples. Figure 5 This will be explained later.

[0039] In this embodiment, the circularity of the tungsten wire 1 is 2.0% or less. That is, the cross section (cross section perpendicular to the wire axis) of the tungsten wire 1 is close enough to a perfect circle. Figure 1 In the figure, the difference between the cross section of the tungsten wire 1 and a perfect circle is exaggerated.

[0040] Here, for the circularity, use Figure 2 Provide explanation. Figure 2 This is a diagram for explaining the circularity. The circularity is an index indicating the deviation of the cross-sectional shape of the tungsten wire 1 from a perfect circle. The smaller the circularity, the smaller the deviation, that is, the closer the cross-sectional shape of the tungsten wire 1 is to a perfect circle. The larger the circularity, the larger the deviation, that is, the further the cross-sectional shape of the tungsten wire 1 is from a perfect circle.

[0041] Specifically, the circularity f (unit: %) is represented by the following formula (1).

[0042] (1) f = (AB) / ((A+B) / 2) × 100

[0043] A and B Figure 2 As shown in . Specifically, first, for the cross section of the tungsten wire 1, the maximum inscribed circle and the minimum circumscribed circle are defined. The maximum inscribed circle and the minimum circumscribed circle are defined so as to be concentric circles and to minimize the interval between them. That is, if the radius of the minimum circumscribed circle is set to r(A) and the radius of the maximum inscribed circle is set to r(B), then r(A)-r(B) becomes the minimum.

[0044] In this case, A is the diameter of the smallest circumscribed circle, which is represented by 2×r(A). B is the diameter of the largest inscribed circle, which is represented by 2×r(B). The circularity f is expressed as a percentage of the difference between the diameter of the smallest circumscribed circle and the diameter of the largest inscribed circle relative to the average value of the diameter of the smallest circumscribed circle and the diameter of the largest inscribed circle, as shown in the above formula (1). If f=0, the smallest circumscribed circle and the largest inscribed circle become identical, so the cross section of the tungsten wire 1 becomes a perfect circle.

[0045] According to the present embodiment, a tungsten wire 1 having a higher tensile strength than before and an optimized roundness (i.e., a cross section close to a perfect circle) corresponding to the wire diameter can be realized. For example, when the tungsten wire 1 is used as a core wire of a saw wire, the thickness variation of the cut object (wafer) can be suppressed by optimizing the roundness. In particular, when the roundness exceeds 2% or 3%, the thickness variation of the wafer, i.e., TTV (Total Thickness Variation), rapidly deteriorates.

[0046] [Manufacturing method]

[0047] Next, in the method for manufacturing the tungsten wire 1 of the present embodiment, the Figure 3 and Figure 4 Provide explanation. Figure 3 and Figure 4 Each of them is a flowchart showing an example of a method for producing the tungsten wire 1 according to the present embodiment.

[0048] like Figure 3 As shown in , first, an additive is added to tungsten (S10). For example, only an additive (doping element) or a compound containing an additive (such as an oxide or an aqueous solution) is added to a predetermined amount of tungsten powder. The doping element is a rare earth element such as rhenium, potassium, or cerium or lanthanum. The useless components contained in the compound are removed by subsequent sintering, etc. The amount of doping element added is adjusted by adding tungsten powder in a predetermined ratio relative to the obtained doped tungsten powder. That is, the doping element can also be added in an amount greater than the content of the target doping element.

[0049] In this way, after adding the doping element to a small amount of tungsten powder, tungsten powder can be added to dilute the doping element (reduce the content). That is, in the doping element adding process, a small amount of the object to be processed can be used, and a small adding device can be used. In addition, since a large amount of doped tungsten powder can be obtained through a single adding process, the number of necessary man-hours of the adding process can be reduced. As a result, the productivity of the tungsten wire 1 can be improved.

[0050] Next, the obtained aggregate of the doped tungsten powder is pressed and sintered to produce a tungsten ingot ( S12 ).

[0051] Next, the produced tungsten ingot is subjected to die forging (S14). Specifically, the tungsten ingot is forged and compressed from the periphery to be stretched and formed into a linear tungsten wire. Instead of die forging, rolling may be performed.

[0052] For example, by repeatedly performing die forging, a tungsten ingot with a diameter of about 15 mm to about 25 mm is formed into a tungsten wire with a wire diameter of about 3 mm to about 4 mm. By performing annealing treatment in the process of die forging, the processability in the subsequent treatment is ensured. For example, annealing treatment is performed at a temperature of 2000°C to 2400°C in the range of 8 mm to 10 mm in diameter. However, in order to ensure the tensile strength by grain refinement, annealing treatment is not performed in the die forging process with a diameter of less than 8 mm.

[0053] Next, the tungsten wire is heated at 900° C. before heat drawing ( S16 ). Specifically, the tungsten wire is directly heated by a burner, etc. By heating the tungsten wire, an oxide layer is formed on the surface of the tungsten wire to prevent the wire from breaking during subsequent heat drawing.

[0054] Next, heated wire drawing is performed (S18). Specifically, the tungsten wire is drawn while being heated using one or more wire drawing dies, i.e., the tungsten wire is drawn (thinned). The heating temperature is, for example, 1000°C. It should be noted that the higher the heating temperature, the higher the processability of the tungsten wire, and therefore the easier it is to draw the wire. The heated wire drawing is repeated while replacing the wire drawing dies. The cross-sectional shrinkage of the tungsten wire produced by one wire drawing using one wire drawing die is, for example, greater than 10% and less than 40%. In the heated wire drawing process, a lubricant obtained by dispersing graphite in water may also be used.

[0055] The heating and drawing are repeated until a tungsten wire of a desired wire diameter is obtained (No in S20). The desired wire diameter is the wire diameter when the number of wire drawing times reaches two remaining times, for example, about 150 μm.

[0056] It should be noted that in the repeated heating wire drawing, a wire drawing die with a smaller hole diameter than the wire drawing die used in the previous wire drawing is used. In addition, in the repeated heating wire drawing, the tungsten wire is heated at a heating temperature lower than the heating temperature in the previous wire drawing. That is, the heating temperature is gradually lowered. The final heating temperature is, for example, 400°C, which helps to refine the grains.

[0057] When the desired tungsten wire diameter is obtained and the remaining number of wire drawing is 2 (Yes in S20), wire drawing is performed at room temperature (S22). Figure 4 As shown in , electrolytic grinding (S21) can also be performed before room temperature drawing (S22). In room temperature drawing, the tungsten wire is drawn without heating, thereby achieving further refinement of the grains. In addition, room temperature drawing also has the effect of aligning the crystal orientation in the processing axis direction (specifically, the direction parallel to the wire axis of the tungsten wire 1).

[0058] The so-called normal temperature is, for example, a temperature in the range of 0°C to 50°C, and as an example, 30°C. Specifically, a plurality of wire drawing dies with different apertures are used to draw the tungsten wire. In normal temperature wire drawing, a water-soluble liquid lubricant is used. Since no heating is performed in normal temperature wire drawing, the evaporation of the liquid can be suppressed. Therefore, it can fully function as a liquid lubricant. Compared with the conventional tungsten wire processing method, i.e., heated wire drawing at a temperature of more than 600°C, by not heating the tungsten wire and processing while cooling with a liquid lubricant, dynamic recovery and dynamic recrystallization can be suppressed, the wire will not break, and it is helpful to refine the grains, and high tensile strength can be obtained.

[0059] The processing rate in room temperature wire drawing is, for example, 70% or more. The processing rate is expressed by the following formula (2) using the wire diameter Db immediately before room temperature wire drawing and the wire diameter Da immediately after room temperature wire drawing.

[0060] (2) Processing rate = {1-(Da / Db) 2}×100

[0061] As can be seen from formula (2), the greater the wire diameter is reduced by normal temperature wire drawing, the greater the processing rate becomes. For example, even if the wire diameter Db just before normal temperature wire drawing is the same, the larger the processing rate, the smaller the wire diameter Da just after normal temperature wire drawing becomes. By increasing the processing rate, the degree of thinning of the tungsten wire produced by normal temperature wire drawing becomes greater, that is, a thinner tungsten wire can be obtained. The processing rate of normal temperature wire drawing is more than 70%, but it can also be more than 80%, more than 90%, or more than 95%. The wire diameter just after normal temperature wire drawing is, for example, in the range of about 50 μm to 120 μm.

[0062] Next, after the room temperature wire drawing, low temperature hot wire drawing (S24) is performed. That is, the final wire drawing of the tungsten wire is performed while heating at a low temperature. The temperature at this time is a temperature higher than the temperature of the room temperature wire drawing (S22) (normal temperature) and lower than the temperature of the heated wire drawing (S18). Specifically, the temperature of the low temperature hot wire drawing is in the range of 100°C to 300°C, and as an example, is 200°C or 300°C. The wire diameter after the low temperature hot wire drawing is, for example, approximately in the range of 20μm to 100μm.

[0063] Finally, the tungsten wire formed by low temperature hot drawing is electrolytically polished to finely adjust the diameter (S26). The electrolytic polishing is performed by, for example, immersing the tungsten wire and the counter electrode in an electrolyte such as sodium hydroxide aqueous solution to generate a potential difference between the tungsten wire and the counter electrode.

[0064] The tungsten wire 1 of this embodiment is manufactured through the above steps. The length of the tungsten wire 1 just manufactured through the above steps is, for example, 50 km or more, and can be used industrially. The tungsten wire 1 can also be cut into appropriate lengths according to the form in which it is used, and used in the shape of a needle or a rod.

[0065] It should be noted that each process shown in the manufacturing method of the tungsten wire 1 is performed online, for example. Specifically, the multiple wire drawing dies used in step S18 are arranged on the production line in the order of decreasing aperture. In addition, a heating device such as a burner is arranged between each wire drawing die. In addition, an electrolytic grinding device may also be arranged between each wire drawing die. On the downstream side (post-process side) of the wire drawing die used in step S18, one or more wire drawing dies used in step S22 and one or more wire drawing dies used in step S24 are arranged in the order of decreasing aperture, and an electrolytic grinding device is arranged on the downstream side of the wire drawing die with the smallest aperture. It should be noted that each process may also be performed individually.

[0066] The above-described method for producing the tungsten wire 1 is merely an example, and the temperature and wire diameter in each step may be adjusted as appropriate.

[0067] As described above, in the manufacturing method of the tungsten wire 1 of the present embodiment, after heat drawing is performed at the first temperature which is a high temperature, normal temperature drawing is performed at the second temperature which is a normal temperature, and then low temperature hot drawing is performed at the third temperature which is a low temperature. The third temperature is higher than the second temperature (normal temperature) and lower than the first temperature (high temperature).

[0068] As described above, the tungsten wire 1 is manufactured by performing a new process called low temperature hot wire drawing (also called low temperature hot working). By performing low temperature hot wire drawing, a tungsten wire 1 with a small wire diameter, high tensile strength, and optimized roundness can be realized.

[0069] [Relationship between tensile strength and wire diameter]

[0070] Next, the relationship between the tensile strength and the wire diameter of the tungsten wire 1 of this embodiment is analyzed using Figure 5 Provide explanation.

[0071] Figure 5 : is a graph showing the relationship between the wire diameter and the tensile strength of the tungsten wire 1 containing rhenium or cerium. Figure 5 In the graph, the horizontal axis represents the wire diameter of the tungsten wire 1 (unit: μm), and the vertical axis represents the tensile strength (unit: MPa).

[0072] The inventors of the present application manufactured a plurality of samples of tungsten wire 1 based on the above-mentioned manufacturing method. The rhenium content (Re content) is adjusted by adjusting the amount of rhenium powder added to the tungsten powder. The wire diameter is adjusted using wire drawing dies with different hole diameters. The tensile strength is an actual value obtained by measuring the tensile strength of the manufactured tungsten wire 1. The tensile strength is measured, for example, based on the tensile test of the Japanese Industrial Standard (JIS H 4460 8). It should be noted that by adjusting the heating temperature and / or processing rate in the wire drawing process, tungsten wires 1 with different tensile strengths can be obtained even with the same Re content and the same wire diameter.

[0073] Will Figure 5 Specific numerical values ​​of Re content, wire diameter, and tensile strength of a plurality of samples of the tungsten wire 1 shown in Tables 1 and 2 are shown.

[0074] Table 1 is a table showing the wire diameter and tensile strength of a tungsten wire 1 containing a predetermined amount of rhenium (Re).

[0075] Table 1

[0076]

[0077] Table 2 is a table showing the tensile strength of the tungsten wire 1 having a wire diameter of 50 μm and 30 μm for each Re content.

[0078] Table 2

[0079]

[0080] like Figure 5 As shown in , there is a negative correlation between the wire diameter and the tensile strength. That is, the smaller the wire diameter, the higher the tensile strength becomes, and the larger the wire diameter, the lower the tensile strength becomes.

[0081] In the tungsten wire 1 of the present embodiment, when the wire diameter is set to D [mm], the range of the following formula (3) is satisfied.

[0082] (3)4758×D 2 -7258.3×D+5275.5≤T≤4758×D 2 -7258.3×D+6100

[0083] The quadratic function on the left side of the inequality in formula (3) is Figure 5 It is represented by the dotted line on the lower side. Figure 5 The dotted line below is obtained by polynomial approximation using the sample with the smallest tensile strength for each wire diameter among the samples in Table 1. The quadratic function on the right side of the inequality of formula (3) is Figure 5 It is represented by the dotted line on the upper side. Figure 5 The upper dotted line is obtained by parallel shifting the above polynomial so that all samples obtained in Table 1 and Table 2 fall between the two dotted lines.

[0084] In addition, Figure 5 , the relationship between the wire diameter and the tensile strength of the tungsten wire 1 containing cerium is also shown. Specific numerical values ​​are shown in Table 3. Table 3 is a table showing the wire diameter and the tensile strength of the tungsten wire 1 containing a predetermined amount of cerium (Ce).

[0085] Table 3

[0086]

[0087] like Figure 5 As shown in Table 3, the tungsten wire 1 containing cerium also satisfies the relationship represented by the above formula (3). Here, cerium is taken as an example, but even if other rare earth elements such as lanthanum (La) having the same characteristics as cerium are contained, the same results can be obtained.

[0088] [Tensile strength and circularity]

[0089] Next, the relationship between the tensile strength and the circularity of the tungsten wire 1 will be described.

[0090] <Containing rhenium (Re)>

[0091] Figure 6 It is a graph showing the relationship between the Re content, the tensile strength and the circularity of a tungsten wire with a wire diameter of 50 μm containing rhenium. Table 4 is a table showing the tensile strength and circularity of a tungsten wire with a wire diameter of 50 μm containing a predetermined amount of rhenium.

[0092] Table 4

[0093]

[0094] like Figure 6 As shown in Table 4, the following tendency is obtained: as the Re content increases from 0.1wt% to 0.5wt%, the tensile strength increases sharply from 5240MPa to 5570MPa, and as the Re content increases from 1.0wt% to 5.0wt%, the tensile strength increases slowly to around 5690MPa. In addition, it is known that as the Re content increases from 0.1wt% to 5wt%, the circularity increases from 0.4% to 2.7% at a roughly constant rate. When the Re content is in the range of 3.0wt% or less, the circularity is 2.0% or less, while when the Re content reaches 5.0wt%, the circularity becomes greater than 2.0%.

[0095] The tungsten wire 1 with a wire diameter of 50 μm of the present embodiment can achieve both a tensile strength of 5200 MPa or more and a roundness of 2.0% or less. In addition, when the Re content is in the range of 0.5 wt % or more and 1.0 wt % or less, a tensile strength of 5500 MPa or more and a roundness of 1.0% or less can be achieved. That is, high tensile strength and more optimized roundness can be achieved.

[0096] Figure 7 It is a graph showing the relationship between the Re content, the tensile strength and the circularity of a tungsten wire with a wire diameter of 30 μm containing rhenium. Table 5 is a table showing the tensile strength and circularity of a tungsten wire with a wire diameter of 30 μm containing a predetermined amount of rhenium.

[0097] Table 5

[0098]

[0099] like Figure 7As shown in Table 5, the following tendency is obtained: as the Re content increases from 0.1wt% to 0.5wt%, the tensile strength increases sharply from 5420MPa to 5770MPa, and as the Re content increases from 1.0wt% to 5.0wt%, the tensile strength increases slowly to 5890MPa. This tendency is the same as the case where the wire diameter is 50μm, but as the wire diameter becomes smaller, the tensile strength becomes higher than the case where the wire diameter is 50μm.

[0100] In addition, it is found that as the Re content increases from 0.1wt% to 5wt%, the circularity increases from 0.3% to 3.2% at a roughly constant rate. When the Re content is in the range of 3.0wt% or less, the circularity is 2.0% or less, while when the Re content reaches 5.0wt%, the circularity becomes greater than 2.0%. This tendency is the same as the case where the wire diameter is 50μm, but the tensile strength increases as the wire diameter decreases, so the increase rate of the circularity becomes larger than the case where the wire diameter is 50μm.

[0101] The tungsten wire 1 with a wire diameter of 30 μm in this embodiment can achieve both a tensile strength of 5400 MPa or more and a roundness of 2.0% or less. In addition, when the Re content is in the range of 0.5 wt % or more and 1.0 wt % or less, a tensile strength of 5750 MPa or more and a roundness of 1.0% or less can be achieved. That is, high tensile strength and more optimized roundness can be achieved.

[0102] As such, it is known that when the Re content is in the range of 0.1wt% to 3.0wt%, the roundness is optimized compared to the past. In addition, when the Re content is in the range of 0.1wt% to 3.0wt%, a higher tensile strength can be achieved. When the Re content is in the range of 0.5wt% to 1.0wt%, both a higher tensile strength and a more optimized roundness can be achieved. It should be noted that by reducing the wire diameter, the tensile strength can be further improved.

[0103] <When Cerium (Ce) is contained>

[0104] Figure 8 It is a graph showing the relationship between the Ce content, the tensile strength and the circularity of a tungsten wire 1 having a wire diameter of 30 μm and containing cerium. Table 6 is a table showing the tensile strength and circularity of a tungsten wire having a wire diameter of 30 μm and containing a predetermined amount of cerium (Ce).

[0105] Table 6

[0106]

[0107] like Figure 8As shown in Table 6, the following tendency is obtained: as the cerium content (Ce content) increases from 0.02wt% to 0.09wt%, the tensile strength increases sharply from 5400MPa to 5730MPa, and as the Ce content increases from 0.09wt% to 0.50wt%, the tensile strength increases slowly to 5920MPa. If the Ce content is 0.03wt% or more, the tensile strength becomes 5500MPa or more. In particular, if the Ce content is 0.30wt% or more, a high tensile strength of 5900MPa or more is achieved.

[0108] In addition, it is known that as the Ce content increases from 0.02wt% to 0.5wt%, the circularity increases from 0.4% to 3.1% at a roughly constant rate. When the Ce content is in the range of 0.30wt% or less, the circularity is 2.0% or less, while when the Ce content is 0.50wt%, the circularity becomes greater than 2.0%. In addition, it is known that when the Ce content is in the range of 0.03wt% or more and 0.09wt% or less, the circularity is 1.0% or less, and the circularity is optimized.

[0109] [Effects, etc.]

[0110] As described above, the tungsten wire 1 of the present embodiment contains tungsten as a main component. When the tensile strength is set to T (unit: MPa) and the wire diameter is set to D (unit: mm), 4758×D 2 -7258.3×D+5275.5≤T≤4758×D 2 -7258.3×D+6100. The circularity of the tungsten wire 1 is 2.0% or less.

[0111] Thus, it is possible to realize a tungsten wire 1 having a higher tensile strength than before in accordance with the wire diameter and having an optimized roundness (that is, having a cross section close to a perfect circle).

[0112] In addition, for example, the tungsten wire 1 may contain rhenium. In this case, the content of rhenium in the tungsten wire 1 is 0.1 wt % or more and 3 wt % or less.

[0113] Thus, it is possible to realize the tungsten wire 1 having an optimized circularity and a higher tensile strength.

[0114] In addition, for example, the tungsten wire 1 may contain a rare earth element. In this case, the content of the rare earth element in the tungsten wire 1 is 0.03 wt % or more and 0.3 wt % or less.

[0115] Thus, it is possible to realize the tungsten wire 1 having an optimized circularity and a higher tensile strength.

[0116] In addition, for example, the content of the rare earth element in the tungsten wire 1 may be 0.03 wt % or more and 0.09 wt % or less. In this case, the circularity of the tungsten wire 1 is 1.0% or less.

[0117] Thus, it is possible to realize the tungsten wire 1 having a more optimized circularity and a higher tensile strength.

[0118] Furthermore, for example, the tensile strength of the tungsten wire 1 is 5800 MPa or more.

[0119] Thus, when the tungsten wire 1 is used as the core wire of the saw wire, the saw wire can be strongly stretched, so that the shaking of the saw wire when cutting the ingot can be suppressed. By suppressing the shaking of the saw wire, the cutting amount of the ingot can be reduced, so the loss can be reduced.

[0120] Furthermore, for example, the tungsten content in the tungsten wire 1 may be 97 wt % or more.

[0121] Furthermore, for example, the wire diameter of the tungsten wire 1 may be 100 μm or less.

[0122] Thus, since the wire diameter is small, when the tungsten wire 1 is used as a saw wire and used for cutting an ingot, for example, the amount of cutting can be reduced, and the number of wafers obtained can be increased.

[0123] Furthermore, for example, the tungsten wire 1 can be used as a core wire of a saw wire.

[0124] Thus, when, for example, an ingot is cut using the tungsten wire 1 with an optimized circularity, the thickness variation of the wafer can be suppressed. That is, wafers with good quality can be manufactured.

[0125] (other)

[0126] As mentioned above, although the tungsten wire of this invention was demonstrated based on the said embodiment, this invention is not limited to the said embodiment.

[0127] For example, the tungsten wire 1 may contain two or more elements selected from rhenium, potassium, and rare earth elements.

[0128] In addition, for example, the tungsten wire 1 can also be used for other than the core wire of the saw wire. For example, the tungsten wire 1 can also be used as the warp and weft of the net. Specifically, a tungsten net is manufactured by weaving the tungsten wire 1. The tungsten net is used for a net for screen printing or scratch-resistant clothing, etc.

[0129] Alternatively, the tungsten wire 1 may be used as a single wire of a twisted wire. Specifically, a twisted wire is manufactured by twisting the tungsten wire 1. The twisted wire is used for ropes, catheters, and the like.

[0130] The tungsten wire 1 can also be used for twisting or knitting with nonwoven fabrics, organic fibers such as nylon, etc. For example, the tungsten wire 1 can be cut to a predetermined length or less and then processed into a nonwoven fabric to produce a nonwoven fabric.

[0131] By optimizing the roundness of the tungsten wire 1, the stress applied to the tungsten wire 1 during processing or use can be easily equalized. That is, it is possible to suppress the application of local large stress to the tungsten wire 1 and suppress the occurrence of wire breakage.

[0132] In addition, the present invention also includes the following methods: methods obtained by implementing various modifications that can be conceived by those skilled in the art to the various embodiments; methods achieved by arbitrarily combining the constituent elements and functions in the various embodiments without departing from the gist of the present invention.

[0133] Explanation of symbols

[0134] 1 Tungsten wire

Claims

1. A tungsten wire comprising tungsten as a main component, When the tensile strength is set to T and the wire diameter is set to D, Meets 4758×D 2 -7258.3×D+5275.5≤T≤4758×D 2 -7258.3×D+6100, The circularity is less than 2.0%. in, The unit of T is MPa, and the unit of D is mm. 2 . The tungsten wire according to claim 1 , comprising rhenium, wherein a content of rhenium in the tungsten wire is greater than or equal to 0.1 wt % and less than or equal to 3 wt %. 3 . The tungsten wire according to claim 1 , comprising a rare earth element, wherein a content of the rare earth element in the tungsten wire is greater than or equal to 0.03 wt % and less than or equal to 0.3 wt %.

4. The tungsten wire according to claim 3, wherein: The content of the rare earth element in the tungsten wire is greater than or equal to 0.03 wt % and less than or equal to 0.09 wt %, and the circularity of the tungsten wire is less than or equal to 1.0%.

5. The tungsten wire according to any one of claims 1 to 4, wherein The tensile strength of the tungsten wire is greater than 5800 MPa.

6. The tungsten wire according to any one of claims 1 to 3, wherein The tungsten content in the tungsten wire is greater than 97 wt %.

7. The tungsten wire according to any one of claims 1 to 4, wherein The wire diameter of the tungsten wire is less than 100 μm.

8. The tungsten wire according to any one of claims 1 to 4, wherein The tungsten wire is used as a core wire of a saw wire.

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