Ultrasonic wire drawing device and method for drawing tungsten wire

Abstract

This invention discloses an ultrasonic wire drawing device and a method for drawing tungsten wire. The device includes a mold frame, which is a hollow tubular structure. From the wire inlet to the wire outlet, it is sequentially divided into a pre-excitation zone, a drawing zone, and a wire outlet zone. Ultrasonic transmission rods are provided on the outer walls of the pre-excitation zone and the drawing zone. A wire drawing die is provided on the inner wall of the drawing zone. A damping layer is provided between the drawing zone and the wire outlet zone, and on the outer side of the wire outlet zone. This device, when applied to drawing tungsten wire, can effectively increase the excitation time of the tungsten wire by ultrasound, thereby overcoming the limitation of existing ultrasonic excitation methods that can only operate at low speeds. It also reduces the wire breakage rate during the tungsten wire drawing process and shortens the process flow.

Description

Technical Field

[0001] This invention relates to a wire drawing device and a method for drawing tungsten wire, and particularly to an ultrasonic tungsten wire drawing process and a wire drawing die device for use with ultrasonic waves, belonging to the field of metal wire drawing technology. Background Technology

[0002] As the primary cutting tool for single-crystal silicon wafers and chemical semiconductor wafers, the raw materials for diamond wire saws mainly include the main wire, diamond micron powder particles, and nickel plating. Currently, the main wire used in diamond wire manufacturing is primarily high-carbon steel wire.

[0003] However, due to the trend towards thinner and larger semiconductor wafers, the diameter and strength of high-carbon steel wire diamond saws are approaching physical limits. For diameters below 35μm, tungsten wire is a good alternative to high-carbon steel wire. Patents such as CN113275659, CN210256788U, and CN109591210 have proposed methods for preparing diamond wire saws based on tungsten wire. However, tungsten has a hardness of 350HB and a tensile strength of 110kg / mm². 2 Tungsten is one of the hardest metals in nature. Although my country's tungsten industry has long been among the world's leading industries, the breakage rate during the production of tungsten wire remains high due to the difficulty of processing it. At the same time, the production process of tungsten wire is characterized by a long production process, high energy consumption, and expensive drawing dies.

[0004] Therefore, reducing the breakage rate in the tungsten wire production process, shortening the tungsten wire production flow, and reducing the wear of the drawing die are of great significance for the development of ultra-fine tungsten wire diamond wire saws and large-size wafers.

[0005] Existing technologies include methods that use ultrasound in conjunction with wire drawing, such as patents CN201198003Y and CN212370840U, which propose widely applicable ultrasonic wire drawing systems. However, for drawing tungsten wires, the following problems still exist:

[0006] (1) The effect of ultrasonic excitation on metal wire drawing is two-sided. On the one hand, ultrasonic excitation can reduce the interlocking effect between the drawing die and the metal wire, enhance the machinability of the metal, and thus reduce the breakage rate. On the other hand, ultrasonic vibration can cause the temperature inside the metal wire to increase. This excitation effect has a beneficial effect on the metal in the deformation zone, but for the metal wire that has already been deformed, it makes its structure more prone to recrystallization, resulting in lower strength and a higher risk of wire breakage.

[0007] (2) Ultrasonic vibration energy only has a significant effect at low drawing speeds. When the time it takes for the metal wire to pass through the drawing die is short, the drawing excitation of the metal wire by the ultrasonic wave can be ignored. Therefore, it is difficult to increase the output. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the first objective of this invention is to provide an ultrasonic wire drawing device that, under ultrasonic coupling, can effectively prevent the increase in internal temperature of the metal wire caused by ultrasound, which could lead to recrystallization of the metal wire structure and a decrease in strength. At the same time, the device can still meet the requirements for high-speed wire drawing under ultrasonic action.

[0009] The second objective of this invention is to provide a method for ultrasonic drawing of tungsten wire. This method, by using the ultrasonic wire drawing device, can effectively reduce the interlocking effect between the tungsten wire and the drawing die wall, reduce the wear of the drawing die, reduce the cost of the drawing die by 40%, and significantly reduce the wire breakage rate. The production process is short and energy consumption is saved.

[0010] To achieve the above-mentioned technical objectives, the present invention provides an ultrasonic wire drawing device, which includes a mold frame; the mold frame is a hollow tubular structure; the mold frame is divided into a pre-excitation zone, a drawing zone, and a wire exit zone from the wire inlet end to the wire outlet end; the outer walls of the pre-excitation zone and the drawing zone of the mold frame are provided with ultrasonic transmission rods; the inner wall of the drawing zone of the mold frame is provided with a wire drawing die; and a damping layer is provided between the drawing zone and the wire exit zone of the mold frame, as well as on the outer side of the wire exit zone.

[0011] The die frame of this invention is divided into a pre-excitation zone, a drawing zone, and a wire exit zone. The pre-excitation zone and the drawing zone are integrated, allowing the metal wire to deform through compression. Simultaneously, by providing ultrasonic transmission rods on the outer walls of the pre-excitation zone and the drawing zone, the ultrasonic vibration energy is utilized to prevent the internal temperature of the metal wire from increasing due to ultrasound, thus avoiding recrystallization of the metal wire structure and resulting in reduced strength. Furthermore, when the metal wire passes through the pre-excitation zone, the effective length of the metal wire in the ultrasonic pre-excitation zone is increased, thereby improving the drawing speed. The drawing die is a common type in the prior art, which can be selected and replaced according to the required diameter of the target metal wire. In addition, by providing damping layers between the drawing zone and the wire exit zone of the die frame, and on the outer side of the wire exit zone, the damping layers absorb the vibration energy of the deformed metal wire, thereby preventing the deformed metal wire from being affected by ultrasonic excitation, thus avoiding recrystallization, reduced strength, and breakage.

[0012] As a preferred embodiment, the pre-excitation zone and drawing zone of the die frame are an integral structure, and the drawing zone and wire exit zone are connected by a mortise and tenon joint. The integral structure of the pre-excitation zone and drawing zone in this invention enables metal deformation and wire drawing. The mortise and tenon joint connecting the drawing zone and wire exit zone is to provide a damping layer between them, preventing the vibration energy from the pre-excitation zone and drawing zone from being transmitted to the die frame in the wire exit zone. This ensures that the fully deformed tungsten wire is not subjected to vibration energy or receives reduced vibration energy, thereby reducing the occurrence of wire breakage.

[0013] As a preferred embodiment, the length of the pre-excitation zone of the die frame is 1 to 1.5 times the length of the drawing zone. In actual use, the length of the pre-excitation zone and the multiple of the drawing zone can be selected within the selected range according to the model of the wire drawing machine and the wire drawing die required for drawing metal wires of different diameters. By extending the length of the pre-excitation zone, the effective length of the metal wire in the ultrasonic pre-excitation zone can be increased, thereby improving the drawing speed.

[0014] As a preferred embodiment, the damping layer is composed of porous felt. The preferred damping layer material of this invention utilizes the structural characteristics of porous felt to absorb ultrasonic vibrations by damping the amplitude within the porous material.

[0015] As a preferred embodiment, the porous felt is at least one of polyester fiber felt, polypropylene fiber felt, alumina fiber felt, aluminum silicate needle-punched felt, or asbestos felt. Aluminum silicate needle-punched felt is more preferred.

[0016] As a preferred embodiment, the thickness of the damping layer 41 in the technical solution of the present invention is 1 to 10 mm, preferably 4 to 10 mm, and the thickness of the damping layer 42 is adjusted according to the process.

[0017] As a preferred embodiment, the compression zone angle of the drawing die is 12 to 14 degrees. The size of the compression zone angle can be selected based on factors such as the size of the tungsten wire.

[0018] The present invention also provides a method for ultrasonic drawing of tungsten wire, wherein the tungsten rod is subjected to rotary forging and molten alkali washing, and then drawn into wire by the ultrasonic wire drawing device described above.

[0019] In the technical solution of this invention, the tungsten rod is first subjected to molten alkaline washing to remove surface microcracks and improve the surface quality of the tungsten rod. Then, the tungsten wire is drawn using the aforementioned ultrasonic wire drawing device. On the one hand, the ultrasonic coupling between the pre-excitation zone and the drawing zone can reduce the interlocking effect between the tungsten wire and the drawing die wall, thereby reducing the wear rate of the drawing die. At the same time, the damping layer also reduces the breakage rate of the tungsten wire. On the other hand, the ultrasonic coupling intensifies the atomic motion inside the tungsten wire, improving the machinability and drawing speed of the tungsten wire, especially enhancing the strength and elongation of the tungsten wire. In addition, ultrasonic coupling enhances the molecular motion of the graphite emulsion during the drawing process, improving its lubrication effect and effectively improving the surface quality of the tungsten wire.

[0020] As a preferred embodiment, the tungsten rod has a diameter of 2-4 mm after rotary forging.

[0021] As a preferred embodiment, the ultrasonic vibration frequency during the wire drawing process is 13–40 kHz, and the vibration amplitude is 10–40 μm.

[0022] As a preferred embodiment, during the wire drawing process, the initial diameter of the tungsten rod is 2-4 mm. It is repeatedly drawn under ultrasonic vibration conditions of 25-40 kHz and vibration amplitude of 20-40 μm until the diameter of the tungsten wire at the exit end reaches less than or equal to 0.25 mm. Then, the drawing process is repeated under vibration conditions of greater than or equal to 13 kHz and less than 25 kHz, and vibration amplitude of greater than or equal to 10 μm and less than 20 μm until the tungsten wire at the exit end reaches the target diameter. In this invention, the higher the vibration frequency, the stronger the vibration energy, the stronger the excitation effect on the tungsten wire, and the better the machinability of the drawn tungsten wire. However, excessively high vibration frequencies will exacerbate the breakage rate during the tungsten wire drawing process. Furthermore, because the strength of a tungsten wire is lower with a smaller diameter, the vibration frequency is relatively lower when the tungsten wire diameter is smaller.

[0023] As a preferred embodiment, the pass reduction rate during the wire drawing process is 14-44.8%. The tungsten wire drawing method of the present invention can increase the pass reduction rate by 1.4-1.6 times compared to the original production process.

[0024] As a preferred embodiment, during the wire drawing process, the initial diameter of the tungsten rod at the feed end is 2–4 mm. The reduction rate per pass during the drawing process is controlled at 39.2–44.8%. When the tungsten rod is drawn to a tungsten wire with a diameter less than or equal to 1.25 mm and greater than 0.1 mm, the reduction rate per pass for further drawing is controlled at 22.4–39.2%. When the tungsten rod is drawn to a tungsten wire with a diameter less than or equal to 0.1 mm, the reduction rate per pass for further drawing is controlled at 10–22.4%. Furthermore, when the total reduction rate reaches 60–85%, annealing treatment is required at 1400–1650 °C for 2–3 minutes. The relationship between the diameter of the tungsten wire or rod at the feed end and the reduction rate per pass was determined by the inventors based on extensive experimental data.

[0025] Compared with existing technologies, the beneficial technical effects of the present invention are as follows:

[0026] 1) The ultrasonic wire drawing device provided by the present invention can avoid the increase in internal temperature of the metal wire caused by ultrasound under the action of ultrasonic coupling, which would cause recrystallization of the metal wire structure and thus reduce the strength. At the same time, the device can still meet the requirements of high-speed wire drawing under the action of ultrasound.

[0027] 2) The ultrasonic drawing method for tungsten wire provided by this invention reduces the interlocking effect between the tungsten wire and the drawing die wall under ultrasonic coupling, effectively reducing die wear, drawing costs, and significantly decreasing the breakage rate. Simultaneously, the increased atomic movement within the tungsten wire improves its machinability, allowing for higher drawing speeds, a 1.4-1.6 times increase in pass reduction, fewer annealing cycles, shorter production processes, and energy savings.

[0028] 3) The wire drawing device of the present invention can effectively increase the strength and elongation of tungsten wire. Attached Figure Description

[0029] Figure 1 This is a cross-sectional view of the ultrasonic pulling device used in Embodiment 1 of the present invention.

[0030] Among them, 1-ultrasonic transmission rod; 2-mold frame; 3-wire drawing mold; 41-first damping layer; 42-second damping layer. Detailed Implementation

[0031] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0032] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0033] Unless otherwise specified, all reagents and raw materials used in this invention are commercially available products or products that can be prepared by known methods.

[0034] Example 1

[0035] The present invention provides an ultrasonic wire drawing device structure as follows: Figure 1As shown. The die frame is a hollow tubular structure; the die frame 2 is divided into a pre-excitation zone, a drawing zone, and a wire exit zone from the wire inlet end to the wire outlet end; the outer walls of the pre-excitation zone and the drawing zone of the die frame 2 are provided with ultrasonic transmission rods 1; the inner wall of the drawing zone of the die frame 2 is provided with a wire drawing die 3; a first damping layer 41 is provided between the drawing zone and the wire exit zone of the die frame 2, and a second damping layer 42 is provided on the outer side of the wire exit zone. The pre-excitation zone and the drawing zone of the die frame are integral structures, which can deform the metal wire through compression. At the same time, by providing ultrasonic transmission rods on the outer walls of the pre-excitation zone and the drawing zone, the effect of ultrasonic vibration energy can be utilized to avoid the increase in internal temperature of the metal wire caused by ultrasound, which would cause recrystallization of the metal wire structure and thus reduce its strength. Moreover, when the metal wire passes through the pre-excitation zone, the action length of the metal wire in the ultrasonic pre-excitation zone is increased, thereby increasing the drawing speed. The drawing zone and the wire exit zone are connected by a tenon and mortise structure. The length of the pre-excitation zone of the die frame is 1.2 times the length of the drawing zone. The damping layer is made of aluminum silicate needle-punched felt, which can effectively absorb the ultrasonic vibration energy of the deformed tungsten wire. The thickness of the first damping layer 41 is 5mm, and the thickness of the second damping layer 42 is 10mm. The compression zone angle of the wire drawing die is 12 degrees.

[0036] The specific steps for using the ultrasonic wire drawing device provided in this embodiment to draw tungsten wire are as follows:

[0037] 1) The tungsten rod is forged using conventional processes, and the diameter after forging is 3mm;

[0038] 2) After the billet is prepared, the tungsten rod is immersed in molten KOH for 3 minutes, washed with water until neutral, dried, and then put into the drawing process.

[0039] 3) A single drawing operation was performed using a chain-type wire drawing machine. The drawing device provided in this embodiment was used as the die frame. The vibration frequency was 38kHz, and the vibration amplitude was 40μm. The reduction rates for each drawing pass were 14% and 19.6%, respectively. The tensile strength of the tungsten rod / wire before and after drawing was tested to obtain the increase in tensile strength. The results are shown in Table 1 below:

[0040] Table 1:

[0041] sample pass reduction rate Tensile strength increment / MPa tungsten rod 14％ 28.6 tungsten wire 16.9％ 54.1

[0042] Example 2

[0043] This embodiment uses a pass reduction rate of 1.4 times that of conventional processes to perform multiple passes of drawing tungsten wire, ultimately obtaining an ultrafine tungsten wire with a diameter of 22μm. No wire breakage occurred during the process, thus demonstrating the engineering applicability of the ultrasonic coupling drawing method for tungsten wire.

[0044] The ultrasonic wire drawing device used in this invention is the same as in Example 1.

[0045] The specific steps for using the ultrasonic wire drawing device provided in this embodiment to draw tungsten wire are as follows:

[0046] 1) The tungsten rod is forged using conventional processes, and the diameter after forging is 3mm;

[0047] 2) After the billet is prepared, the tungsten rod is immersed in molten KOH for 3 minutes, washed with water until neutral, dried, and then put into the drawing process.

[0048] 3) The processed tungsten rod is drawn using a chain wire drawing machine (the drawing device provided in this embodiment is used as the die frame). The ultrasonic vibration frequency is 38kHz and the vibration amplitude is 40μm. The pass reduction rate is 44.8%, and it is drawn to 1.25mm after 2 passes.

[0049] 4) The above tungsten wire is drawn to 0.78 mm in one pass using an MB2500 wire drawing machine with an ultrasonic vibration frequency of 32 kHz, a vibration amplitude of 33 μm, and a pass reduction rate of 37.6%.

[0050] 5) The above tungsten wire is subjected to stress-relief annealing at 1500℃ for 2 minutes.

[0051] 6) After annealing, the tungsten wire is drawn through an MB1000 wire drawing machine with an ultrasonic vibration frequency of 29kHz, a vibration amplitude of 25μm, and a pass reduction rate of 33.6%. It is drawn to 0.43mm in 2 passes.

[0052] 7) The above tungsten wire is drawn to 0.1 mm in 5 passes using an MB500 wire drawing machine with an ultrasonic vibration frequency of 25 kHz, a vibration amplitude of 20 μm, and a pass reduction rate of 28%.

[0053] 8) The above tungsten wire is subjected to stress-relief annealing at 1500℃ for 2 minutes.

[0054] 9) The above tungsten wire is drawn to 0.03mm in 7 passes using a C7301 wire drawing machine with an ultrasonic vibration frequency of 13kHz, a vibration amplitude of 10μm, and a pass reduction rate of 16.8%.

[0055] 10) The above tungsten wire is drawn through a C7303 wire drawing machine with an ultrasonic vibration frequency of 13kHz, a vibration amplitude of 10μm, and a pass reduction rate of 14%. It is drawn to 0.025mm in 1 pass and to 0.022mm in 2 passes.

[0056] This embodiment saves at least 7 steps compared to the conventional process, reduces the number of annealing processes by 2, ensures a good surface condition of the tungsten wire during the drawing process, eliminates the need for alkaline washing, and prevents wire breakage.

[0057] Example 3

[0058] The ultrasonic wire drawing device used in this invention is the same as in Example 1.

[0059] The specific steps for using the ultrasonic wire drawing device provided in this embodiment to draw tungsten wire are as follows:

[0060] 1) The tungsten rod is forged using conventional processes, and the diameter after forging is 3mm;

[0061] 2) After the billet is prepared, the tungsten rod is immersed in molten KOH for 3 minutes, washed with water until neutral, dried, and then put into the drawing process.

[0062] 3) The processed tungsten rod is drawn using a chain wire drawing machine (the drawing device provided in this embodiment is used as the die frame). The ultrasonic vibration frequency is 40kHz and the vibration amplitude is 35μm. The pass reduction rate is 40%, and the rod is drawn to 1.25mm after 2 passes.

[0063] 4) The above tungsten wire is drawn to 0.78 mm in one pass using an MB2500 wire drawing machine with an ultrasonic vibration frequency of 35 kHz, a vibration amplitude of 29 μm, and a pass reduction rate of 37.6%.

[0064] 5) The above tungsten wire is subjected to stress-relief annealing at 1500℃ for 2 minutes.

[0065] 6) After annealing, the tungsten wire is drawn through an MB1000 wire drawing machine with an ultrasonic vibration frequency of 30kHz, a vibration amplitude of 23μm, and a pass reduction rate of 32%. It is then drawn to 0.43mm in 2 passes.

[0066] 7) The above tungsten wire is drawn to 0.25mm in 2 passes using an MB500 wire drawing machine with an ultrasonic vibration frequency of 27kHz, a vibration amplitude of 20μm, and a pass reduction rate of 26%.

[0067] 8) The above tungsten wire is drawn to 0.1 mm in 3 passes using an MB500 wire drawing machine with an ultrasonic vibration frequency of 23 kHz, a vibration amplitude of 17 μm, and a pass reduction rate of 26%.

[0068] 9) The above tungsten wire is subjected to stress-relief annealing at 1500℃ for 2 minutes.

[0069] 10) The above tungsten wire is drawn to 0.03mm in 7 passes using a C7301 wire drawing machine with an ultrasonic vibration frequency of 15kHz, a vibration amplitude of 12μm, and a pass reduction rate of 15%.

[0070] 11) The above tungsten wire is drawn to 0.024 mm in 2 passes using a C7303 wire drawing machine with an ultrasonic vibration frequency of 14 kHz, a vibration amplitude of 11 μm, and a pass reduction rate of 10%.

[0071] This embodiment saves at least 7 steps compared to the conventional process, reduces the number of annealing processes by 2, ensures a good surface condition of the tungsten wire during the drawing process, eliminates the need for alkaline washing, and prevents wire breakage.

[0072] Comparative Example 1

[0073] The specific steps for drawing tungsten wire using the conventional wire drawing die device provided in this comparative embodiment are as follows:

[0074] 1) The tungsten rod is forged using conventional processes, and the diameter after forging is 3mm;

[0075] 2) After the billet is prepared, the tungsten rod is immersed in molten KOH for 3 minutes, washed with water until neutral, dried, and then put into the drawing process.

[0076] 3) Use a chain wire drawing machine to perform one drawing (using a common wire drawing die), with a reduction rate of 10% and 14% per pass, respectively. Perform tensile strength tests on the tungsten rod / wire before and after drawing to obtain the increase in tensile strength. The results are shown in Table 2 below.

[0077] Table 2:

[0078] sample pass reduction rate Tensile strength increment / MPa tungsten rod 10％ 30.7 tungsten wire 14％ 56.55

[0079] A comparison of the data from Example 1 and Comparative Example 1 shows that the reduction rate per pass in Comparative Example 1 without the wire drawing die device of the present invention is lower than that in Example 1. Furthermore, the tensile strength increments of the tungsten rod and tungsten wire in Comparative Example 1 are higher than those in Example 1. The larger the tensile strength increment, the more severe the work hardening and the faster the machinability decreases. This indicates that when the wire drawing device of the present invention is used, the rate of decrease in the machinability of the tungsten wire is slowed down.

[0080] Comparative Example 2 (Conventional Process)

[0081] This embodiment uses conventional wire drawing equipment to perform multiple drawing passes on the same batch of tungsten rods, ultimately obtaining ultrafine tungsten wires with a diameter of 31 μm. However, when the diameter is below 31 μm, the tungsten wires break during drawing. The specific steps are as follows:

[0082] 1) The tungsten rod is forged using conventional processes, and the diameter after forging is 3mm;

[0083] 2) After the billet is prepared, the tungsten rod is immersed in molten KOH for 3 minutes, washed with water until neutral, dried, and then put into the drawing process.

[0084] 3) The processed tungsten rod is drawn by a chain wire drawing machine (the die frame is a common die frame on the market), with a pass reduction rate of 32%, and is drawn to 1.25mm after 3 passes.

[0085] 4) The above tungsten wire is subjected to stress-relief annealing at 1500℃ for 2 minutes.

[0086] 5) The above tungsten wire is drawn through an MB2500 wire drawing machine with a pass reduction rate of 28%, and is drawn to 0.78mm in 2 passes.

[0087] 6) The above tungsten wire is drawn through an MB1000 wire drawing machine with a pass reduction rate of 24%, and is drawn to 0.43mm in 3 passes.

[0088] 7) The above tungsten wire is subjected to stress-relief annealing at 1500℃ for 2 minutes.

[0089] 8) The above tungsten wire is drawn to 0.27 mm in 2 passes using an MB500 wire drawing machine with a reduction rate of 20%. It is then subjected to stress-relief annealing at 1500℃ for 2 minutes and then drawn to 0.11 mm in 4 passes with a reduction rate of 20%.

[0090] 9) The above tungsten wire is subjected to stress-relief annealing at 1500℃ for 2 minutes.

[0091] 10) The above tungsten wire was drawn through a C7301 wire drawing machine with a pass reduction rate of 14%, and was drawn to 0.031mm in 11 passes. During the process, the tungsten wire broke.

[0092] The comparative example underwent 25 passes and 4 annealing processes. The surface condition of the tungsten wire was good during the initial drawing process, but the wire broke at 0.031 mm.

[0093] The results of comparing Example 2 and Example 2 fully demonstrate that the present invention can reduce the breakage rate during the wire drawing process and shorten the tungsten wire production process.

Claims

1. A method for ultrasonically drawing tungsten wire, characterized in that: After the tungsten rod is forged and molten alkaline washed, it is drawn into wire using an ultrasonic wire drawing device. The ultrasonic vibration frequency during the wire drawing process is 13~40kHz, and the vibration amplitude is 10~40μm; During the wire drawing process, the initial diameter of the tungsten rod is 2-4 mm. It is repeatedly drawn under ultrasonic vibration frequency of 25-40 kHz and vibration amplitude of 20-40 μm until the diameter of the tungsten wire at the wire exit end reaches less than or equal to 0.25 mm. Then, it is changed to repeated drawing under vibration frequency of greater than or equal to 13 kHz and less than 25 kHz and vibration amplitude of greater than or equal to 10 μm and less than 20 μm until the tungsten wire at the wire exit end reaches the target diameter.

2. The method for ultrasonic drawing of tungsten wire according to claim 1, characterized in that: The ultrasonic wire drawing device includes a mold frame; the mold frame is a hollow tubular structure; the mold frame is divided into a pre-excitation zone, a drawing zone, and a wire exit zone from the wire inlet end to the wire outlet end; the outer walls of the pre-excitation zone and the drawing zone of the mold frame are provided with ultrasonic transmission rods; the inner wall of the drawing zone of the mold frame is provided with a wire drawing die; a damping layer is provided between the drawing zone and the wire exit zone of the mold frame, and on the outer side of the wire exit zone.

3. The method for ultrasonic drawing of tungsten wire according to claim 2, characterized in that: The pre-excitation zone and the drawing zone of the mold frame are integral structures, and the drawing zone and the wire exit zone are connected by a mortise and tenon structure.

4. A method for ultrasonically drawing tungsten wire according to claim 2 or 3, characterized in that: The length of the pre-excitation zone of the mold frame is 1 to 1.5 times the length of the drawing zone.

5. The method for ultrasonically drawing tungsten wire according to claim 4, characterized in that: The shock-absorbing layer is composed of porous felt; The porous felt is at least one of polyester fiber felt, polypropylene fiber felt, alumina fiber felt, aluminum silicate needle-punched felt, or asbestos felt.

6. The method for ultrasonically drawing tungsten wire according to claim 2, characterized in that: The compression zone angle of the wire drawing die is 12~14 degrees.

7. The method for ultrasonic drawing of tungsten wire according to claim 1, characterized in that: The reduction rate per pass during the wire drawing process is 14-44.8%.

8. The method for ultrasonically drawing tungsten wire according to claim 7, characterized in that: During the wire drawing process, the initial diameter of the tungsten rod at the feed end is 2-4 mm. The reduction rate per pass during the wire drawing process is controlled at 39.2-44.8%. When the tungsten rod is drawn to a tungsten wire with a diameter less than or equal to 1.25 mm and greater than 0.1 mm, the reduction rate per pass for the next draw is controlled at 22.4-39.2%. When the tungsten rod is drawn to a tungsten wire with a diameter less than or equal to 0.1 mm, the reduction rate per pass for the next draw is controlled at 10-22.4%. When the total reduction rate reaches 60-85%, annealing treatment is required at 1400-1650℃ for 2-3 minutes.

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