Metal wire, cutting wire with high tensile strength and manufacturing process thereof

Abstract

The application discloses a metal wire with high tensile strength, a cutting wire and a metal wire manufacturing process, and relates to the technical field of metal wires. The metal wire manufacturing process comprises powder preparation, ingot preparation, forging processing, ordinary wire drawing and large compression ratio wire drawing. No annealing is performed in the large compression ratio wire drawing process, so that the particle size of additive particles is refined, and tungsten grain growth caused by annealing is avoided. The dislocation density for refining the additive particles is not reduced, and the additive particles can be refined through wire drawing processing. The large compression ratio wire drawing adopts the mode of increasing the average cross-section shrinkage rate, a larger compressive stress is applied to the inside of the tungsten wire, the additive particle size can be refined at the same time as the generation of voids is inhibited, and the target outer diameter and tensile strength are obtained.

Description

Technical Field

[0001] This invention relates to the field of metal wire technology, and more specifically, to a metal wire with high tensile strength, a cutting wire, and a metal wire manufacturing process. Background Technology

[0002] Previously, metal wires with tungsten as the main component were mainly used as filaments for light bulbs or fluorescent lamps. However, in recent years, due to the high strength and elastic modulus of tungsten, it has also been used as the core wire for cutting wires.

[0003] In recent years, significant progress has been made in the development of technologies to improve the tensile strength of tungsten-based metal wires used as core wires in silicon ingot cutting. However, while increasing tensile strength, the drawing stress during wire drawing also increases the porosity within the metal wire, making it more prone to breakage during silicon ingot cutting. Wire breakage during cutting can cause substantial losses, such as reduced quality of the cut silicon wafers, equipment downtime, and lost labor time required to restart the system. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to provide a metal wire with high tensile strength, a cutting wire, and a metal wire manufacturing process.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a metal wire with high tensile strength, wherein the metal wire comprises tungsten and additives, and the mass fraction of tungsten is greater than 50%; In a cross-section perpendicular to the axis of the metal wire, the particle size of the additive particles is less than 0.1% of the outer diameter of the metal wire, and the porosity is less than 4%.

[0006] A further technical solution of this application is: the outer diameter of the metal wire is greater than 11μm and less than 60μm, and the tensile strength of the metal wire is greater than 5000MPa.

[0007] A further technical solution of this application: when the metal wire is subjected to a tension of 70% of its tensile strength and is wound and replaced, the wire breakage rate is less than once per 200 kilometers.

[0008] This application also provides a cutting wire, with the aforementioned metal wire as the core wire.

[0009] This application also provides a manufacturing process for a metal wire with high tensile strength, used to manufacture the aforementioned metal wire, comprising the following steps: Powder preparation, ingot preparation, forging, conventional wire drawing and high compression ratio wire drawing.

[0010] A further technical solution of this application is: the powder preparation is to prepare tungsten powder in which the particle size and amount of tungsten and additives meet the requirements.

[0011] A further technical solution of this application: the ingot preparation involves shaping and sintering tungsten powder to produce an ingot.

[0012] A further technical solution of this application: The forging process is to perform groove and roll processing and rotary forging on the ingot to obtain a metal wire with an outer diameter greater than 3mm and less than 5mm.

[0013] A further technical solution of this application: The ordinary wire drawing process uses multiple dies with different apertures to gradually reduce the outer diameter of the metal wire to 770μm, and then gradually reduces the outer diameter of the metal wire to 390μm.

[0014] A further technical solution of this application: The high compression ratio wire drawing is to use multiple dies with different apertures to draw the metal wire, first processing the outer diameter of the metal wire from 390μm to 179μm, and the average cross-sectional shrinkage rate of the metal wire reaches more than 19.7% and less than 20.2%. The outer diameter of the metal wire is then processed from 179μm to 80μm through wire drawing, and the average cross-sectional shrinkage rate of the metal wire reaches more than 18.0% and less than 18.5%. Finally, the outer diameter of the metal wire is processed from 80μm to between 11μm and 60μm through wire drawing. The average cross-sectional shrinkage rate of the metal wire reaches more than 15.8% and less than 16.3%. The generation of voids is suppressed by applying large compressive stress to the inside of the metal wire.

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. In the high compression ratio wire drawing process of the present invention, annealing is not performed, thereby refining the particle size of the additive particles and avoiding tungsten grain growth caused by annealing. The dislocation density used to refine the additive particles will not decrease, and the additive particles can be refined by wire drawing. 2. The high compression ratio wire drawing of the present invention adopts the method of increasing the average cross-sectional shrinkage rate. By applying a large compressive stress to the inside of the tungsten wire, it is possible to refine the particle size of the additives while suppressing the generation of voids, thereby obtaining the target outer diameter and tensile strength, and thus reducing the probability of wire breakage during the cutting process.

[0016] 3. By eliminating the annealing process, this invention reduces one step and the number of molds required, thus achieving energy-efficient production.

[0017] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Specific embodiments of the present invention are given in detail below with reference to the accompanying drawings. Attached Figure Description

[0018] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a process flow diagram of machining the outer diameter of the metal wire to 390μm in an embodiment of the present invention; Figure 2 This is a flowchart of the existing process for machining the outer diameter of the metal wire to 30μm in an embodiment of the present invention; Figure 3 This is a flowchart of the high compression ratio process for machining the outer diameter of the metal wire to 30μm in an embodiment of the present invention; Figure 4 This is a line graph showing the experimental examples and comparative examples in the embodiments of the present invention; Figure 5 This is a SEM image of the cross section at 50,000x magnification from Experiment Example 4 in this embodiment of the invention. Figure 6 This is a SEM image of the cross section at 50,000x magnification for Comparative Example 4 in this embodiment of the invention. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] In the description of the embodiments of the present invention, it should be noted that if terms such as "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" appear to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0021] The embodiments shown below are specific examples of the present invention. The numerical values, materials, constituent elements, configuration of constituent elements, and order of steps shown in the embodiments are all examples and are not intended to limit the present invention.

[0022] Reference Figures 1 to 6 In one embodiment of this application, a high tensile strength metal wire is provided. The metal wire comprises tungsten and additives. The tungsten has a mass fraction greater than 50%, which should be understood as the tungsten mass fraction being 90% or more, 95% or more, 99.2% or more, 99.4% or more, 99.6% or more, or 99.9% or more. The additives include potassium and / or rare earth elements. The potassium has a mass fraction greater than 0.001% and less than 0.009%, and the rare earth elements have a mass fraction greater than 0.02% and less than 0.8%. Additives can increase the primary recrystallization temperature and tensile strength. Additives include potassium, rare earth elements, and potassium and rare earth elements. The mass fraction of potassium can be above 0.003% or above 0.005%, and the mass fraction of rare earth elements can be above 0.03%, above 0.05%, above 0.1%, or above 0.2%. Whether it's potassium or rare earth elements, the amount added can be increased to improve the target tensile strength; however, the upper limit of potassium mass fraction is below 0.009%. If too much potassium is added, the metal wire will become brittle and its processability will deteriorate; the upper limit of rare earth element mass fraction is below 0.8%. If too much rare earth element is added, the metal wire will become hard and its processability will deteriorate. In the cross section (cross-section) of the metal wire perpendicular to the wire axis, the particle size of the additive particles is less than 0.1% of the outer diameter of the metal wire, or less than 0.08% or less, and the porosity is less than 4%. That is, the particle size of the additive particles is less than 25 nanometers in a metal wire with a diameter of 30 μm, and less than 20 nanometers in a metal wire with a diameter of 25 μm.

[0023] Metal wires may contain unavoidable elements mixed in during the manufacturing process, such as iron, chromium, nickel, and molybdenum, or solid solution strengthening elements such as rhenium.

[0024] In a preferred embodiment of this application, the outer diameter of the metal wire is greater than 11 μm and less than 60 μm, for example, 13 μm, 15 μm, 18 μm, 25 μm, 30 μm, 40 μm or 50 μm, and the tensile strength of the metal wire is greater than 5000 MPa; Increasing the amount of potassium or rare earth elements can improve the tensile strength of metal wires to over 5500 MPa, over 6000 MPa, over 6500 MPa, over 7000 MPa, or over 7500 MPa.

[0025] As a preferred embodiment of this application, when the metal wire is subjected to a tension of 70% of its tensile strength and is wound and replaced, the wire breakage rate is less than once per 200 kilometers.

[0026] In another embodiment of this application, a cutting wire is also proposed, which uses the aforementioned metal wire as the core wire of the cutting wire, thereby obtaining a cutting wire with high tensile strength and suppressed porosity, which can reduce the probability of wire breakage during the cutting process.

[0027] In another embodiment of this application, a manufacturing process for a metal wire with high tensile strength is also proposed, comprising the following steps: Powder preparation, ingot preparation, forging, conventional wire drawing and high compression ratio wire drawing.

[0028] In one embodiment, the powder preparation involves preparing tungsten powder in which the particle size and amount of tungsten and additives both meet the requirements.

[0029] In one embodiment, the ingot preparation involves shaping and sintering tungsten powder to produce an ingot.

[0030] In one embodiment, the ingot preparation involves shaping and sintering tungsten powder to produce an ingot.

[0031] In one embodiment, the ordinary wire drawing process involves using multiple dies with different apertures to gradually reduce the outer diameter of the metal wire to 770 μm, and then gradually reducing the outer diameter of the metal wire to 390 μm.

[0032] like Figure 1 This is a typical manufacturing process for metal wire with tungsten as the main component, processed to 390 μm. Tungsten powder with controlled tungsten particle size and the particle size and amount of additives is prepared. Afterwards, it is shaped and sintered to produce an ingot. The next process is forging, which includes grooving and rotary forging. The outer diameter is machined to between 3 mm and 5 mm through forging. After forging, multiple dies with different apertures are prepared, and the outer diameter is gradually reduced to 770 μm through wire drawing. Then, multiple dies with even smaller apertures are prepared to gradually reduce the outer diameter to 390 μm.

[0033] like Figure 2This refers to an existing manufacturing process for machining metal wires with an outer diameter of 390 μm down to 30 μm. In this process, a 390 μm diameter metal wire is annealed at approximately 1400°C, resulting in a recrystallization that significantly increases the growth of tungsten grains refined through machining. This process alleviates internal stress to prevent wire breakage when machining the wire down to 30 μm. This annealing process reduces the tensile strength by more than 5% compared to before annealing. After annealing the 390 μm diameter metal wire, multiple dies with different apertures are prepared to achieve an average section reduction rate of 17.5% to 18.0%, and the wire is then machined down to an outer diameter of 180 μm. Subsequently, multiple dies with different apertures are prepared to achieve an average section reduction rate of 16.0% to 16.5%, and the wire is machined down to an outer diameter of 80 μm. Next, prepare multiple molds with different apertures to achieve an average cross-sectional shrinkage rate of 13.5% or more and 14.0% or less, and process them to an outer diameter of, for example, 30 μm.

[0034] Section shrinkage rate = 1 - (outer diameter after drawing)² / (outer diameter before drawing)².

[0035] In one embodiment, the high compression ratio wire drawing is performed by drawing the metal wire using dies with multiple different apertures. The outer diameter of the metal wire is first processed from 390μm to 179μm, and the average cross-sectional shrinkage rate of the metal wire reaches more than 19.7% and less than 20.2%. The outer diameter of the metal wire is then processed from 179μm to 80μm through wire drawing, and the average cross-sectional shrinkage rate of the metal wire reaches more than 18.0% and less than 18.5%. Finally, the outer diameter of the metal wire is processed from 80μm to between 11μm and 60μm through wire drawing. The average cross-sectional shrinkage rate of the metal wire reaches more than 15.8% and less than 16.3%. The generation of voids is suppressed by applying large compressive stress to the inside of the metal wire.

[0036] like Figure 3This describes a manufacturing process for machining a metal wire with an outer diameter of 390 μm to 30 μm for the purpose of implementing this invention. First, for a metal wire with an outer diameter of 390 μm, without annealing, multiple dies with different apertures are prepared, and the average section shrinkage rate is increased to 19.7% to 20.2%, and the wire is machined to an outer diameter of 179 μm. The purpose of machining without annealing is to refine the particle size of the additive particles. If annealing causes tungsten grain growth, the dislocation density used to refine the additive particles will decrease, making it difficult to refine the additive particles through wire drawing. Next, similarly, multiple dies with different apertures are prepared, and the average section shrinkage rate is increased to 18.0% to 18.5%, and the wire is machined to an outer diameter of 80 μm. Then, multiple dies with different apertures are prepared, and the average section shrinkage rate is increased to 15.8% to 16.3%, and the wire is machined to, for example, an outer diameter of 30 μm. The reason for increasing the average reduction of section ratio compared to conventional manufacturing processes is to suppress the formation of voids by applying greater compressive stress to the interior of the tungsten wire. However, increasing the average reduction of section ratio when voids have already formed can lead to wire breakage during the drawing process. Therefore, in the initial stage of processing, i.e., when the outer diameter of the metal wire is 390 μm, it is necessary to significantly increase the average reduction of section ratio. This process can refine the particle size of the additives while suppressing void formation, achieving the target outer diameter and tensile strength. Electrolytic polishing can be performed on the surface during or at the end of the drawing process. A coating can also be formed on the surface during or at the end of the drawing process.

[0037] The evaluation method for porosity and additive particle size is based on SEM observation of a cross-section perpendicular to the wire axis. Porosity is calculated through image processing.

[0038] The evaluation method for wire breakage during ingot cutting involves conducting a breakage test while the metal wire is being wound and replaced under a certain tension. This certain tension is 70% of the tensile strength of the metal wire. During ingot cutting, the tension borne by the metal wire is between 60% and 70% of its tensile strength; therefore, a similar tension is applied for the test.

[0039] Table 1 shows the adjustments to the amount of additives, according to... Figure 1 After being processed to an outer diameter of 390μm, they were respectively processed according to... Figure 3 and Figure 2 The process involves processing the metal wire using a specific technique, and then evaluating the tensile strength, the porosity in the cross-section perpendicular to the wire axis, the particle size of the additives, and the breakage when the metal wire is wound under a certain tension. For both the comparative and experimental examples, the machining process to an outer diameter of 390 μm was the same. The subsequent machining of the comparative examples used... Figure 2The existing process in the experiment used the following subsequent processing: Figure 3 The process of this invention. Additionally... Figure 4 This is a graph based on the results in Table 1, with tensile strength on the horizontal axis and porosity on the vertical axis.

[0040] Table 1: Experimental Examples and Comparative Examples As shown in Table 1 and Figure 4 As shown, in the comparative examples, the porosity increased sharply with the increase of tensile strength. This is because the drawing stress during wire drawing increases with the increase of tensile strength, thus forming voids. The larger the particle size of the additive particles, the easier it is to generate voids starting from the additive particles. On the other hand, in the experimental examples, although the porosity also increased with the increase of tensile strength, it was more gradual compared to the comparative examples. As shown in Table 1, the porosity of Experimental Example 4 was 2.3% when the tensile strength was 6580 MPa, which was lower than the 2.8% porosity of Comparative Example 3 when the tensile strength was 6010 MPa. Furthermore, in Experimental Examples 1 to 5, the particle size of the additive particles was less than 0.1% of the outer diameter of the metal wire.

[0041] Regarding the wire breakage tests in Table 1, all tests used 200 km of metal wire. In Experimental Examples 1 to 4, no wire breakage occurred during tests applying a tension equivalent to 70% of the tensile strength. On the other hand, Comparative Example 4 experienced three wire breakages during the 200 km test. The amount of metal wire required for one ingot cut is approximately 10 km; 200 km of metal wire can be used for 20 cuts, but if three breakages occur, the breakage rate reaches 15%. The typical breakage rate during silicon ingot cutting is between 10% and 20%. The good breakage performance in the experimental examples is due to the ability to reduce porosity and, by refining the particle size of the additives to less than 0.1% of the outer diameter, to suppress damage originating from the additive particles and the expansion of voids under sustained stress.

[0042] Figure 5 This is an example of a SEM image of a section perpendicular to the axis of the line in Experiment 4, magnified at 50,000 times. Figure 6 This is an example of a SEM image of a section perpendicular to the axis of the line in Comparative Example 4, magnified at 50,000 times.

[0043] The representative fracture morphology in the wire breakage test was cup-shaped fracture, which confirms the formation of voids within the metal wire. To suppress wire breakage during the cutting process, it is important to refine the particle size of the additives and suppress the increase in porosity.

[0044] In addition to the advantage of suppressing wire breakage during the cutting process, the embodiments of the present invention also have the advantage of reducing production costs. The first advantage is that eliminating annealing reduces one process step and enables energy-efficient production. The second advantage relates to the number of molds used. In conventional manufacturing processes, approximately 30 molds are required to process from a diameter of 390 μm to 30 μm, while in the process of the embodiments of the present invention, only 26 molds are needed.

[0045] The present invention has been described based on the above embodiments, but the present invention is not limited to the described embodiments. For example, the manufacturing process is not limited to... Figure 3 The process illustrated is merely an example. The manufacturing process is intended to obtain the particle size and porosity of the target additive particles, and to suppress wire breakage during use. Furthermore, the drawing method can be heated drawing, room temperature drawing, or a combination of both. In addition, various modifications that can be conceived by those skilled in the art are also included in this invention.

[0046] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A metal wire with high tensile strength, characterized in that, The metal wire comprises tungsten and additives, wherein the tungsten has a mass fraction of more than 90%, and the additives include potassium and / or rare earth elements, wherein the potassium has a mass fraction of more than 0.001% and less than 0.009%, and the rare earth elements have a mass fraction of more than 0.02% and less than 0.8%. In a cross-section perpendicular to the axis of the metal wire, the particle size of the additive is less than 0.1% of the outer diameter of the metal wire, and the porosity is less than 4%. The manufacturing process of the metal wire includes the following steps: Powder preparation, metal ingot preparation, forging, conventional wire drawing and high compression ratio wire drawing; No annealing is performed during the high compression ratio fiber drawing process; The metal ingot preparation involves shaping and sintering tungsten powder to produce metal ingots; The high compression ratio wire drawing process involves using dies with different apertures to draw the metal wire, first reducing the outer diameter of the metal wire from 390μm to 179μm, and achieving an average cross-sectional shrinkage rate of over 19.7% and below 20.2%. The outer diameter of the metal wire is then reduced from 179μm to 80μm by drawing, and the average cross-sectional shrinkage rate of the metal wire reaches more than 18.0% and less than 18.5%. Finally, the outer diameter of the metal wire is processed from 80μm to between 11μm and 60μm through wire drawing. The average cross-sectional shrinkage rate of the metal wire reaches more than 15.8% and less than 16.3%. The generation of voids is suppressed by applying large compressive stress to the inside of the metal wire.

2. The high tensile strength metal wire according to claim 1, characterized in that: The tensile strength of the metal wire is greater than 5000 MPa.

3. The high tensile strength metal wire according to claim 2, characterized in that: When the metal wire is subjected to a tension of 70% of its tensile strength and is wound and replaced, the breakage rate is less than once per 200 kilometers.

4. A cutting line, characterized in that, The metal wire described in any one of claims 1-3 is used as the core wire.

5. A manufacturing process for a high tensile strength metal wire, used to manufacture the metal wire according to any one of claims 1-3, characterized in that, Includes the following steps: Powder preparation, metal ingot preparation, forging, conventional wire drawing and high compression ratio wire drawing; No annealing is performed during the high compression ratio fiber drawing process; The metal ingot preparation involves shaping and sintering tungsten powder to produce metal ingots; The high compression ratio wire drawing process involves using dies with different apertures to draw the metal wire, first reducing the outer diameter of the metal wire from 390μm to 179μm, and achieving an average cross-sectional shrinkage rate of over 19.7% and below 20.2%. The outer diameter of the metal wire is then reduced from 179μm to 80μm by drawing, and the average cross-sectional shrinkage rate of the metal wire reaches more than 18.0% and less than 18.5%. Finally, the outer diameter of the metal wire is processed from 80μm to between 11μm and 60μm through wire drawing. The average cross-sectional shrinkage rate of the metal wire reaches more than 15.8% and less than 16.3%. The generation of voids is suppressed by applying large compressive stress to the inside of the metal wire.

6. The manufacturing process for high tensile strength metal wire according to claim 5, characterized in that: The powder preparation refers to the preparation of tungsten powder in which the particle size and amount of tungsten and additives meet the requirements.

7. The manufacturing process for high tensile strength metal wire according to claim 5, characterized in that: The forging process involves grooving and rotary forging of a metal ingot to obtain a metal wire with an outer diameter greater than 3 mm and less than 5 mm.

8. The manufacturing process for high tensile strength metal wire according to claim 7, characterized in that: The conventional wire drawing process involves using multiple dies with different apertures to gradually reduce the outer diameter of the metal wire to 770 μm, and then further reducing it to 390 μm.

Images