Ultrasonic-assisted nickel-titanium alloy fine filament drawing device and method

Abstract

The invention discloses a device and method for drawing a nickel-titanium alloy micro-filament with the assistance of ultrasonic waves. The device comprises a one-way stretching mechanism, an ultrasonic vibration mechanism and a centering drawing mechanism. The one-way stretching mechanism comprises a cross beam and a base. The ultrasonic vibration mechanism is fixedly connected with the base and comprises an ultrasonic transducer, a first fastener and a drawing die. The centering drawing mechanism is fixedly connected with the cross beam and comprises a winch assembly, a bidirectional fine adjustment assembly and a rigid connecting plate which are sequentially arranged in the first direction. The bidirectional fine adjustment assembly comprises a first platform, a middle platform and a second platform, and a first adjusting part is connected between the first platform and the middle platform and used for driving the middle platform to move in the second direction; and a second adjusting piece is connected between the second platform and the middle platform. According to the device and the method, stable drawing of the nickel-titanium alloy wire with the diameter smaller than 100 microns can be achieved, a force signal in the drawing process can be accurately measured, the high single-pass area reduction rate and the low wire breakage rate are achieved, the intermediate annealing procedure is omitted, and energy consumption is reduced.

Description

TECHNICAL FIELD

[0001] The present specification relates to the technical field of metal micro-wire processing, and in particular to a device and method for using ultrasonic assisted drawing of nickel-titanium alloy micro-wire. BACKGROUND

[0002] Nickel-titanium alloy is widely used in medical devices (such as cardiovascular stents, guide wires) and micro-electro-mechanical systems due to its unique shape memory effect and super-elasticity. These applications often require nickel-titanium alloy wires to be extremely thin (diameter less than 100 μm) and have excellent surface quality and mechanical properties.

[0003] Currently, multi-pass cold drawing technology is mainly used to prepare extremely thin nickel-titanium alloy wires. However, as the wire diameter decreases to the micron scale, two major problems arise during the drawing process: first, surface effects are intensified, and the friction between the wire and the die accounts for a significant proportion of the total drawing force, making it extremely easy to break the wire with the same high reduction ratio as thick wires; second, nickel-titanium alloy work hardening is severe, and traditional drawing requires multiple intermediate annealing to restore plasticity, which increases the production process and energy consumption, and may cause wire surface oxidation and grain coarsening, affecting the final performance. SUMMARY

[0004] The inventors have found that ultrasonic vibration assisted drawing technology has been proven to effectively reduce the drawing force and is expected to solve the above problems. However, existing ultrasonic drawing devices have the following limitations in research and use: 1. For micro-wires with a diameter of less than 100 μm, it is extremely difficult to ensure neutralization during drawing, and even a slight deviation can cause the wire to be sheared and broken; 2. There is a lack of a dedicated test platform that can simultaneously and accurately measure the drawing force of micro-wires and observe the ultrasonic effect; 3. The influence of ultrasonic process parameters (such as amplitude and frequency) on the drawing process of ultra-fine wires is not clear, and there is a lack of systematic research methods to optimize the process, making it difficult to fully utilize the potential of ultrasonic assistance to achieve high reduction ratio, save annealing process, and reduce energy consumption.

[0005] In view of the deficiencies of the prior art, one object of the present specification is to provide a device and method for using ultrasonic assisted drawing of nickel-titanium alloy micro-wire, which can achieve stable drawing of nickel-titanium alloy wires with a diameter of less than 100 μm, accurately measure the force signal during drawing, achieve high single-pass reduction ratio and low breakage rate, and save intermediate annealing process and reduce energy consumption.

[0006] To achieve the above object, the embodiments of the present specification provide a device for using ultrasonic assisted drawing of nickel-titanium alloy micro-wire, comprising: The unidirectional stretching mechanism for providing the drawing force comprises a crossbeam and a base; the base is fixedly arranged, and the crossbeam is driven to move in a first direction by the drawing force; The ultrasonic vibration mechanism fixedly connected with the base comprises an ultrasonic transducer, a first fastener and a drawing die; the drawing die is fixedly connected to a top-end cavity of a horn of the ultrasonic transducer through the first fastener, and the ultrasonic transducer is used for applying high-frequency vibration to the drawing die; the drawing die and the first fastener are both provided with a through hole for the wire to pass through; and the ultrasonic vibration mechanism is used for fixing one end of the wire. The centering and drawing mechanism fixedly connected with the crossbeam comprises a winch assembly, a bidirectional fine adjustment assembly and a rigid connection plate arranged in sequence in a first direction; the rigid connection plate is fixedly connected with the crossbeam; the bidirectional fine adjustment assembly comprises a first platform, an intermediate platform and a second platform; the first platform is fixedly connected with the rigid connection plate, the intermediate platform is slidably fixedly connected with the first platform in a second direction, the intermediate platform is slidably fixedly connected with the second platform in a third direction, and the second platform is fixedly connected with the winch assembly; the first direction, the second direction and the third direction are perpendicular to each other; a first adjusting member is connected between the first platform and the intermediate platform and used for driving the intermediate platform to move relative to the first platform in the second direction; a second adjusting member is connected between the second platform and the intermediate platform and used for driving the second platform to move relative to the intermediate platform in the third direction; and the winch assembly is provided with a second fastener for fixing the other end of the wire.

[0007] As a preferred embodiment, the drawing die is cylindrical, the first fastener is a fastening nut, the drawing die is fixed in the top-end cavity of the horn through the pre-tightening force generated by the fastening nut and the first screw thread in the top-end cavity of the horn, the ultrasonic transducer makes the drawing die reciprocate in the first direction, and the ultrasonic transducer is provided with a circular through hole in the center for the wire to pass through.

[0008] As a preferred embodiment, the ultrasonic vibration mechanism further comprises a first winding drum, a transducer clamping plate, a height-increasing support and a first connection plate; the first winding drum is used for winding the wire to be processed; two transducer clamping plates are symmetrically arranged, fixed to the height-increasing support by bolts and clamp the outer wall of the ultrasonic transducer; the height-increasing support is fixed to the first connection plate by bolts to provide mounting space for the first winding drum; the first connection plate is provided with a second screw thread and a first pin hole, which are used for fixing the ultrasonic vibration mechanism to a universal interface of the base of the unidirectional stretching mechanism; and the base is located below the crossbeam.

[0009] As a preferred embodiment, the frequency of the ultrasonic vibration output by the ultrasonic transducer is 38 kHz or 41 kHz.

[0010] As a preferred embodiment, the rigid connecting plate comprises a second pin hole and a third thread for fixing the centering and drawing mechanism to the universal interface of the unidirectional stretching mechanism beam; the first platform is fixed to the rigid connecting plate through a pre-set threaded hole; the first platform is provided with a first guide rail extending in the second direction, and the intermediate platform is adjusted in the second direction by rotating the first adjusting member along the first guide rail; the intermediate platform is provided with a second guide rail extending in the third direction, and the second platform is adjusted in the third direction by rotating the second adjusting member along the second guide rail; the second platform is fixed to the winch assembly through a pre-set threaded hole.

[0011] As a preferred embodiment, the winch assembly comprises a frame, a stepper motor, a shaft coupling, a mandrel, a second winding drum and a bearing; the second winding drum is rigidly connected to the mandrel, one end of the mandrel is fixedly connected to the shaft coupling, and the other end is rotatably connected to the frame through the bearing; the second fastener is a fixed bolt, a threaded hole is provided on the winding drum, the wire is wound on the fixed bolt and screwed into the fixed bolt, and the pre-tightening force of the fixed bolt forms a stable clamping of the wire between the head of the fixed bolt and the outer wall of the second winding drum; the stepper motor is fixed to the frame through a pre-set threaded hole, and the torque output end of the stepper motor is rigidly connected to the shaft coupling for driving the mandrel and the second winding drum to rotate.

[0012] As a preferred embodiment, the surface material of the second winding drum is rubber or metal.

[0013] As a preferred embodiment, the wire collecting speed of the winch assembly is 1 mm / s to 300 mm / s.

[0014] As a preferred embodiment, the mass of the centering and drawing platform is less than or equal to 2.1 kg.

[0015] The application also provides a method for using ultrasonic-assisted drawing of nickel-titanium alloy micro-wire, which uses the device for using ultrasonic-assisted drawing of nickel-titanium alloy micro-wire according to any one of the above embodiments, and comprises the following steps: One end of the nickel-titanium alloy thick wire is passed through the drawing die and fixed to the winch assembly; The unidirectional stretching mechanism is started, the beam drives the centering and drawing mechanism to move in the first direction, and the nickel-titanium alloy thick wire is drawn; the wire axis is accurately centered with the axis of the drawing die by observing the force sensor reading of the unidirectional stretching mechanism and finely adjusting the bidirectional fine adjustment assembly; During the drawing process, the ultrasonic transducer of the ultrasonic vibration mechanism is turned on; The change of the drawing force before and after the ultrasonic transducer is turned on is recorded and analyzed by the unidirectional stretching mechanism; wherein the drawing force can be reduced by 30% to 50% after the ultrasonic transducer is turned on. Advantages

[0016] The device and method for drawing nickel-titanium alloy micro wires with ultrasonic assistance provided by the embodiment have the following advantages: 1. High stability and centration: By rigidly connecting the centration drawing mechanism and the crossbeam of the unidirectional stretching mechanism and setting a bidirectional fine adjustment assembly, the centration problem of micro wire drawing is fundamentally solved, the wire breakage rate of wire materials with a diameter of less than 100 μm is significantly reduced, and stable drawing is achieved. In particular, the centration drawing platform is designed to be lightweight, with a total weight of about 2.1 kg, which greatly reduces the load requirement of the crossbeam of the tensile testing machine, so that the device can be adapted to widely used small and medium-sized high-precision unidirectional tensile testing machines, and can capture the change of drawing force caused by ultrasonic vibration in real time and accurately.

[0017] 2. Significant reduction of drawing force and improvement of surface quality: experimental data show that the drawing force can be reduced by 30% to 50% after the ultrasonic vibration is turned on. SEM image comparison shows that the surface of the wire drawn with ultrasonic assistance is smoother, and the scratches and surface defects are significantly reduced.

[0018] 3. Achieving high reduction rate and low wire breakage rate: under the assistance of ultrasonic vibration, the device and method can achieve severe plastic deformation with a single pass reduction rate of up to 40% without breaking the wire. This is higher than the reduction rate limit of traditional micro wire drawing, significantly reduces the overall wire breakage rate, and improves the production efficiency.

[0019] 4. Providing a new method of reducing energy consumption and saving process: compared with the existing mature micro wire drawing method with multiple passes, small reduction rate and the need for multiple annealing, the present application provides a new energy-saving and efficient way based on ultrasonic assistance with high single pass reduction rate and without intermediate annealing.

[0020] Specific embodiments of the application are disclosed in detail in the following description and accompanying drawings, indicating the ways in which the principles of the application can be employed. It should be understood that the embodiments of the application are not limited in scope by the embodiments described, since the embodiments are intended as illustrations of the principles of the application.

[0021] Features described and / or illustrated with respect to one embodiment can be used in the same or similar way in one or more other embodiments, in combination with or in place of features in other embodiments.

[0022] It should be emphasized that the term "comprises / comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description only constitute some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from these drawings without creative labor.

[0024] Figure 1 Fig. 1 is a structural schematic diagram of an ultrasonic vibration mechanism provided in the present embodiment; Figure 2 Fig. 2 is a side view of Fig. 1; Figure 1 Figure 3 Fig. 3 is a structural schematic diagram of a centering drawing mechanism provided in the present embodiment; Figure 4 Fig. 4 is a right view of Fig. 3; Figure 3 Figure 5 Fig. 5 is a scanning electron microscope image of a surface of a wire drawn by a method of the present application using ultrasonic assistance, and a surface of a wire drawn by a method without ultrasonic assistance.

[0025] Explanation of Reference Signs: 1, ultrasonic vibration mechanism; 11, ultrasonic transducer; 12, first fastener; 13, drawing die; 14, first winding drum; 15, transducer clamping plate; 16, heightening support; 17, first connecting plate; 171, second screw thread; 172, first pin hole; 2, centering drawing mechanism; 21, winch assembly; 211, second fastener; 212, frame; 213, stepping motor; 214, shaft coupling; 215, mandrel; 216, second winding drum; 217, bearing; 22, bidirectional fine adjustment assembly; 221, first platform; 222, intermediate platform; 223, second platform; 224, first adjustment member; 225, second adjustment member; 23, rigid connecting plate; 231, second pin hole; 232, third screw thread; 3, wire; X, first direction; Y, second direction; Z, third direction. DETAILED DESCRIPTION

[0026] ​​In order to make the technical solutions in the present application better understood by those skilled in the art, the technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts should fall within the protection scope of the present application.

[0027] It should be noted that when an element is referred to as being "disposed on" another element, it can be directly on the other element or there can be another element interposed. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or there can be another element interposed. The terms "vertical", "horizontal", "left", "right", and similar expressions used herein are for illustrative purposes only and are not intended to be limiting.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0029] Please refer to Figures 1 to 4 The embodiment of the present application provides a device for drawing a micro-nickel titanium alloy wire with ultrasonic assistance, which comprises a unidirectional stretching mechanism (not shown in the figure), an ultrasonic vibration mechanism 1 and a centering drawing mechanism 2.

[0030] The unidirectional stretching mechanism is used to provide a drawing force and comprises a crossbeam and a base. The base is fixedly arranged, and the crossbeam is driven to move in a first direction X by the drawing force. The base is located below the crossbeam. The unidirectional stretching mechanism in the embodiment of the present application can be selected from the unidirectional stretching experimental machines in the prior art, and specifically, an MTS E44.104-B type unidirectional stretching experimental machine can be selected. The unidirectional stretching mechanism can provide stable stretching power and accurately measure the drawing force.

[0031] As shown in Figure 1 and Figure 2 The ultrasonic vibration mechanism 1 is fixedly connected with the base and comprises an ultrasonic transducer 11, a first fastener 12 and a drawing die 13. The drawing die 13 is fixedly connected in a cavity at a top end of a variable amplitude rod of the ultrasonic transducer 11 through the first fastener 12, and the ultrasonic transducer 11 is used to apply high-frequency vibration to the drawing die 13. The drawing die 13 and the first fastener 12 are both provided with through holes for the wire material 3 to pass through. The ultrasonic vibration mechanism 1 is used to fix one end of the wire material 3.

[0032] As shown in Figure 3 and Figure 4 The centering drawing mechanism 2 is fixedly connected with the crossbeam, and includes a winch assembly 21, a bidirectional fine adjustment assembly 22 and a rigid connecting plate 23 arranged in sequence in a first direction X. The centering drawing mechanism 2 is used for precisely centering and winding and drawing the wire 3. The rigid connecting plate 23 is fixedly connected with the crossbeam, so that the crossbeam can drive the centering drawing mechanism 2 to move, and the centering drawing mechanism 2 can move synchronously with the crossbeam. The bidirectional fine adjustment assembly 22 includes a first platform 221, an intermediate platform 222 and a second platform 223, which are used for adjusting the position of the centering drawing mechanism 2 relative to the drawing die 13, and more specifically, adjusting the spatial position of the winch assembly 21 relative to the center through hole of the drawing die 13, so as to ensure that the ejection direction of the wire 3 during the drawing process is always parallel to the axis of the drawing die 13. The first platform 221 is fixedly connected with the rigid connecting plate 23, the intermediate platform 222 is slidably fixedly connected with the first platform 221 in a second direction Y, the intermediate platform 222 is slidably fixedly connected with the second platform 223 in a third direction Z, and the second platform 223 is fixedly connected with the winch assembly 21. The first direction X, the second direction Y and the third direction Z are perpendicular to each other. Specifically, the first direction X can be a vertical direction, and the second direction Y and the third direction Z are two directions perpendicular to each other in a horizontal plane. Figures 1 to 4 The drawing direction of the wire 3 in the device is vertically upward.

[0033] A first adjusting member 224 is connected between the first platform 221 and the intermediate platform 222, and is used for driving the intermediate platform 222 to move along the second direction Y relative to the first platform 221. A second adjusting member 225 is connected between the second platform 223 and the intermediate platform 222, and is used for driving the second platform 223 to move along the third direction Z relative to the intermediate platform 222. The winch assembly 21 is provided with a second fastening member 211, which is used for fixing the other end of the wire 3.

[0034] The device for drawing a micro-wire of a nickel-titanium alloy with ultrasonic assistance provided by the embodiment has the following advantages: 1. High stability and centering: by rigidly connecting the centering drawing mechanism 2 with the crossbeam of the uniaxial tensile testing machine and arranging the bidirectional fine adjustment assembly 22, the centering problem of the micro-wire drawing is fundamentally solved, the wire breakage rate of the wire 3 with a diameter of less than 100 μm is significantly reduced, and stable drawing is achieved. In particular, the centering drawing platform is designed to be lightweight, with a total weight of about 2.1 kg, which greatly reduces the load requirement of the crossbeam of the tensile testing machine, so that the device can be adapted to widely used small and medium-sized high-precision uniaxial tensile testing machines, and can accurately capture the change of the drawing force caused by ultrasonic vibration in real time.

[0035] 2. Significant reduction of drawing force and improvement of surface quality: Experimental data show that the drawing force can be reduced by 30%~50% after turning on the ultrasonic vibration. SEM image comparison shows that the wire 3 surface using ultrasonic assisted drawing is smoother, and the scratches and surface defects are significantly reduced.

[0036] 3. Achieving high reduction rate and low wire breakage rate: Under the assistance of ultrasonic vibration, the device and method of the application can achieve severe plastic deformation with a single pass reduction rate of up to 40% without breaking the wire. This is higher than the reduction rate limit of traditional micro-wire drawing, significantly reducing the overall wire breakage rate and improving production efficiency.

[0037] 4. Provide a new method of reducing energy consumption and saving process: Compared with the existing mature multi-pass, small reduction rate, and multiple annealing micro-wire drawing method, the application provides a new energy-saving and efficient way based on high single-pass reduction rate and without intermediate annealing.

[0038] In this embodiment, the drawing die 13 is cylindrical. The first fastener 12 is preferably a fastening nut, and the drawing die 13 is fixed in the top cavity of the amplitude rod by the pre-tightening force generated by the rotation of the first thread in the fastening nut and the top end of the amplitude rod. A circular hole is reserved in the middle of the fastening nut for the wire 3 to pass through the end of the drawing die 13. The ultrasonic transducer 11 makes the drawing die 13 reciprocate along the first direction X (i.e. the axial direction of the wire 3). The center of the ultrasonic transducer 11 is provided with a circular hole for the wire 3 to pass through.

[0039] As shown in Figure 1 and Figure 2 , the ultrasonic vibration mechanism 1 further comprises a first winding drum 14, a transducer clamping plate 15, a height increasing support 16, and a first connecting plate 17, which can vertically arrange the ultrasonic transducer 11 on the base below the crossbeam of the uniaxial stretching mechanism and temporarily store the wire 3 to be drawn.

[0040] Specifically, the first winding drum 14 is used to wind the wire 3 to be processed, can rotate freely, and can temporarily store the wire 3 to be processed to prevent the wire 3 from knotting and ensure the stability of long-term testing. Two transducer clamping plates 15 are symmetrically arranged, fixed on the height increasing support 16 by bolts, and clamp the outer wall of the ultrasonic transducer 11. The height increasing support 16 can lift the transducer clamping plate 15, and the height increasing support 16 is fixed on the first connecting plate 17 by bolts to provide installation space for the first winding drum 14. The first connecting plate 17 is provided with a second thread 171 and a first pin hole 172 for fixing the ultrasonic vibration mechanism 1 to the universal interface of the base of the uniaxial stretching mechanism.

[0041] Preferably, the frequency of the ultrasonic vibration output by the ultrasonic transducer 11 is 38 kHz or 41 kHz.

[0042] In this embodiment, as shown in Figure 4As shown, the rigid connecting plate 23 includes a second pin hole 231 and a third threaded hole 232 for fixing the centering and drawing mechanism 2 to the universal interface of the uniaxial stretching mechanism beam. The first platform 221 is fixed to the rigid connecting plate 23 through a pre-set threaded hole; the first platform 221 is provided with a first guide rail extending in the second direction Y, and the intermediate platform 222 is adjusted in the second direction Y position by rotating the first adjusting member 224 to drive the intermediate platform 222 along the first guide rail; the intermediate platform 222 is provided with a second guide rail extending in the third direction Z, and the second platform 223 is adjusted in the third direction Z position by rotating the second adjusting member 225 to drive the second platform 223 along the second guide rail; the second platform 223 is fixed to the winch assembly 21 through a pre-set threaded hole.

[0043] As shown in Figure 3 and Figure 4 The winch assembly 21 includes a frame 212, a stepping motor 213, a shaft coupling 214, a mandrel 215, a second winding drum 216 and a bearing 217. The second winding drum 216 is rigidly connected to the mandrel 215, one end of the mandrel 215 is fixedly connected to the shaft coupling 214, and the other end is rotatably connected to the frame 212 through the bearing 217. The second fastener 211 is a fixed bolt, and the wire 3 is wound around the fixed bolt and screwed into the fixed bolt. The pre-tightening force of the fixed bolt forms a stable clamping of the wire 3 between the head of the fixed bolt and the outer wall of the second winding drum 216.

[0044] The stepping motor 213 is fixed to the frame 212 through a pre-set threaded hole, and the torque output end of the stepping motor 213 is rigidly connected to the shaft coupling 214 for driving the mandrel 215 and the second winding drum 216 to rotate. Specifically, a stepping motor 213 with a product model of MS42DDC can be selected, which has a rated torque of 86 mN·m and a rated speed of 285 rpm.

[0045] Further, the adjustment accuracy of the bidirectional fine adjustment assembly 22 is preferably 0.01 mm. The first adjusting member 224 and the second adjusting member 225 are preferably rotary adjusting handles.

[0046] Specifically, the surface material of the second winding drum 216 is rubber-coated or metal (e.g. 45 steel) to adapt to different ultrasonic auxiliary amplitudes.

[0047] In this embodiment, the wire collecting speed of the winch assembly 21 is preferably 1 mm / s~300 mm / s.

[0048] Specifically, the centering and drawing platform adopts a lightweight design, and its mass is less than or equal to 2.1 kg to minimize the additional load on the uniaxial stretching mechanism beam.

[0049] The embodiment of the present application also provides a method for drawing a nickel-titanium alloy micro-wire by using ultrasonic assistance, which uses the device for drawing a nickel-titanium alloy micro-wire by using ultrasonic assistance according to any one of the above embodiments, and the details of the related content are described in the device part above, which will not be repeated here.

[0050] In the embodiment of the method, the technical problems solved by the device embodiment can be solved, and the technical effects of the device embodiment can be achieved, and the details of the present application will not be repeated here.

[0051] The method for drawing a nickel-titanium alloy micro-wire by using ultrasonic assistance comprises the following steps (step S10, step S20, step S30, step S40): Step S10: One end of a nickel-titanium alloy thick wire is passed through the drawing die 13 and fixed to the winch assembly 21. Further, the second drum 216 fixed to the winch assembly 21.

[0052] Before step S10, a sample preparation work also needs to be performed. Specifically, a commercial nickel-titanium alloy wire with a diameter of 0.1 mm is selected. First, a conventional solid solution annealing process (600°C, 10 min) is used to pretreat the wire material 3 to eliminate historical work hardening and obtain a uniform coarse-grained austenitic structure. Subsequently, the oxidation layer at the tip of the wire material 3 is removed by sanding, and the end of the wire material 3 is subjected to etching sharpening treatment to facilitate subsequent drawing operation.

[0053] In step S10, one end of the annealed nickel-titanium alloy thick wire can be passed through the drawing die 13 at the top end of the amplitude rod of the ultrasonic transducer 11 and fixed to the second drum 216 of the winch assembly 21 by tightening the fixing bolt. The material of the drawing die 13 is diamond, and the hole diameter is 0.08 mm.

[0054] More specifically, the wire material 3 is uniformly coated with a lubricant, and the sharpened end is passed through the drawing die 13 and fixed to the second drum 216 of the winch assembly 21, then the drawing die 13 is fixed at the top end of the amplitude rod of the ultrasonic transducer 11, and the tightening nut is tightened. Subsequently, the winch assembly 21 and the ultrasonic transducer 11 are fixed to the crossbeam and the base of the unidirectional stretching mechanism using the pins.

[0055] Step S20: Start the unidirectional stretching mechanism to move the centering drawing mechanism 2 along the first direction X driven by the crossbeam to draw the nickel-titanium alloy thick wire. By observing the force sensor reading of the unidirectional stretching mechanism and finely adjusting the bidirectional fine adjustment assembly 22, the axis of the wire material 3 is accurately centered with the axis of the through hole of the drawing die 13.

[0056] In step S20, the unidirectional stretching mechanism is started, the crossbeam drives the centering and drawing mechanism 2 to slowly rise at a speed of 0.5 mm / s, the preliminary drawing state is observed, the second drum 216 is finely adjusted by using the bidirectional fine adjustment assembly 22, until the drawing force is stable, indicating that the wire 3 is well centered.

[0057] Step S30: In the drawing process, the ultrasonic transducer 11 of the ultrasonic vibration mechanism 1 is turned on.

[0058] Step S40: The change of the drawing force before and after the ultrasonic transducer 11 is turned on is recorded and analyzed by the unidirectional stretching mechanism (including the drop value and oscillation of the drawing force). After the ultrasonic transducer 11 is turned on, the drawing force can be reduced by 30% to 50%.

[0059] In step S30, the drawing speed is set, the position of the crossbeam of the unidirectional stretching mechanism is fixed, the hoisting mechanism is started for drawing, and after the drawing force is stable, the ultrasonic vibration mechanism 1 is turned on. The drawing speed after centering is set to 2 mm / s. After the drawing force is stable at about 4.5 N, the ultrasonic vibration mechanism 1 is turned on, and the power is adjusted to 20 W. The force sensor records that the drawing force drops significantly in an instant and is accompanied by high-frequency micro-oscillation, and finally stabilizes at about 2.6 N, with a drawing force drop of 40%. In this process, the single-pass area reduction is about 36% (from a diameter of 0.1 mm to a diameter of 0.08 mm), and no wire breakage occurs.

[0060] By comparing the changes of the drawing force and the surface quality of the wire 3 under different ultrasonic parameters (power, amplitude), the optimal process window is determined. Using the optimized process, the nickel-titanium alloy wire with a diameter of less than 100 μm can be stably drawn at a single-pass area reduction of up to about 36%, and the wire breakage rate is significantly reduced.

[0061] In order to verify the improvement of the surface quality by ultrasonic vibration, comparative experiments are carried out under the same process parameters (area reduction of 40%, speed of 2 mm / s) without turning on the ultrasonic and turning on the ultrasonic (100 W). The surfaces of the wires 3 drawn in the two groups are observed by using a scanning electron microscope (SEM). As shown in the results of FIGS. 8A and 8B, the surface of the wire 3 drawn without using ultrasonic assistance has obvious longitudinal scratches and micro-tears, and the surface quality is not good. As shown in FIG. 8A, the surface of the wire 3 drawn by using ultrasonic assistance is significantly smooth and uniform, and the defects such as scratches are basically eliminated, and the surface quality is fundamentally improved. Figure 5 Figure 5 As shown in FIG. 8B. Figure 5

[0062] ​​Based on the above-mentioned optimized ultrasonic parameters (100W), the device is continuously used to draw the wire 3 from a diameter of 0.08mm to a diameter of 0.07mm (the reduction rate of this pass is about 25%). The wire 3 is drawn from a diameter of 0.07mm to a diameter of 0.06mm (the reduction rate of this pass is about 26%) using the same ultrasonic parameters. During the whole multi-pass drawing process from a diameter of 0.1mm to a diameter of 0.06mm (the total reduction rate is 64%), no intermediate annealing treatment is implemented. The finally obtained diameter 0.06mm ultra-fine wire is smooth in surface and free of cracks.

[0063] Under the assistance of ultrasonic vibration, the drawing can be realized without intermediate annealing, the total reduction rate reaches 64%, the minimum wire diameter reaches 60μm, the single-pass reduction rate reaches 36% at the highest, and the wire breakage rate is significantly reduced.

[0064] In the initial stage of drawing, the relative position between the hoisting assembly 21 and the hole of the drawing die 13 is adjusted by the bidirectional fine adjustment assembly 22, so that the drawing force tends to be stable, the wire 3 is accurately centered, and the wire breakage rate in the ultrasonic vibration process is reduced.

[0065] The effect of ultrasonic vibration on reducing the drawing force and the friction is evaluated by analyzing the drop value and the oscillation signal of the drawing force. After the ultrasonic is turned on, the drawing force is reduced by 30%-50%, and the surface smoothness of the wire 3 drawn with the assistance of ultrasonic vibration is better than that of the wire 3 drawn without the assistance of ultrasonic vibration.

[0066] The device and method for drawing nickel-titanium alloy ultra-fine wire with the assistance of ultrasonic vibration provided by the embodiments of the present application are special for ultra-fine wire, especially nickel-titanium alloy ultra-fine wire, to break through the process limitation of traditional drawing, i.e., multi-pass, small reduction rate and the need for multiple annealing.

[0067] It should be noted that, in the description of the present specification, the terms "first", "second", etc. are only used for the purpose of description and distinguishing similar objects, and there is no sequence between them, nor can it be understood or implied as relative importance. In addition, in the description of the present specification, unless otherwise stated, the meaning of "multiple" is two or more.

[0068] Any numerical values recited herein include all values from the lower value and up to the upper value in increments of one unit, provided that there is a separation of at least 2 units between any lower value and any higher value. As an example, if a numerical value is recited as being from 1 to 90, preferably from 20 to 80, and more preferably from 30 to 70, it is intended that values such as 15 to 85, 22 to 68, 43 to 51, and 30 to 32, etc. are expressly enumerated in this specification. For values which are less than one, one unit is considered to be 0.0001, 0.001, 0.01, 0.1, as appropriate. These are only examples of what is specifically enumerated herein, and are not meant to limit the application in any way. Furthermore, the inclusion of a numerical range recited herein is not intended to exclude any gyrations from the scope of the range, as appropriately interpreted.

[0069] Unless otherwise stated, all ranges include both endpoints and all numbers between the endpoints. "Approximately" or "about" when used before a range or a value means that the value falls within a range of plus or minus ten percent of the value.

[0070] All articles and references, including patents and publications, disclosed herein are incorporated herein by reference for all purposes. The term "consisting essentially of to describe a combination shall include the elements, ingredients, components or steps identified, and such other elements ingredients, components or steps that do not materially affect the basic and novel characteristics of the combination. The use of the term "comprising" or "including" to describe combinations of elements, ingredients, components or steps herein also is taken to mean that other elements, ingredients, components or steps can be present in addition to those specifically recited, in order to achieve the described functionality of the combination. The term "may" when used in a permissive sense (i.e. as an

[0071] Multiple elements, ingredients, components or steps can be provided by a single integrated element, ingredient, component or step. Alternatively, a single integrated element, ingredient, component or step might be divided into separate multiple elements, ingredients, components or steps. To "comprise" or "comprising", or "include" or "including" or "has" or "having" or "contain" or "containing" or "consist" or "consisting" or "consisting essentially of" as used herein, can vary between "open" and "closed" transitions, and are intended to be equivalent in meaning to "comprising" or "including", or "has", "having", "contain", "containing", "consist", "consisting" or "consisting essentially of", as those terms are used in either the open-ended or the closed transitional sense.

[0072] It is to be understood that the above description is intended to be illustrative, and not restrictive. Many embodiments and many applications other than the examples provided would be apparent upon reading the above description. The scope of the teachings should, therefore, be determined not with reference to the above description, but should instead be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. The disclosures of all articles and references, including patent applications and publications, are incorporated by reference for all purposes. The omission in the following claims of any aspect of subject matter that is disclosed herein is not a disclaimer of such subject matter, nor should it be regarded that the inventors did not consider such subject matter to be part of the disclosed inventive subject matter.

Claims

1. An apparatus for ultrasonic assisted drawing of a nickel-titanium alloy micro wire, characterized by, The application relates to a wire drawing device. The device comprises a unidirectional stretching mechanism for providing a drawing force, a ultrasonic vibration mechanism fixedly connected with the base, and a centering drawing mechanism fixedly connected with the beam. The unidirectional stretching mechanism comprises a beam and a base; the base is fixedly arranged, and the beam is driven to move in a first direction by the drawing force. The ultrasonic vibration mechanism comprises an ultrasonic transducer, a first fastener and a drawing die; the drawing die is fixedly connected to a top-end cavity of a variable amplitude rod of the ultrasonic transducer through the first fastener, and the ultrasonic transducer is used for applying high-frequency vibration to the drawing die; the center of the drawing die and the first fastener are provided with through holes for the wire to pass through; and the ultrasonic vibration mechanism is used for fixing one end of the wire.

2. The apparatus for use in ultrasonic-assisted drawing of a micro-wire of nickel-titanium alloy according to claim 1, characterized in that, The centering drawing mechanism comprises a winch assembly, a bidirectional fine adjustment assembly and a rigid connecting plate arranged in sequence in a first direction; the rigid connecting plate is fixedly connected with the beam; the bidirectional fine adjustment assembly comprises a first platform, an intermediate platform and a second platform; the first platform is fixedly connected with the rigid connecting plate; the intermediate platform is slidably fixedly connected with the first platform in a second direction; the intermediate platform is slidably fixedly connected with the second platform in a third direction; the second platform is fixedly connected with the winch assembly; the first direction, the second direction and the third direction are perpendicular to each other; a first adjusting member is connected between the first platform and the intermediate platform and used for driving the intermediate platform to move relative to the first platform in the second direction; a second adjusting member is connected between the second platform and the intermediate platform and used for driving the second platform to move relative to the intermediate platform in the third direction; and the winch assembly is provided with a second fastener for fixing the other end of the wire.

3. The apparatus for use in ultrasonic-assisted drawing of a micro-wire of nickel-titanium alloy according to claim 1, characterized in that, The ultrasonic vibration mechanism further comprises a first winding drum, transducer clamping plates, a height-increasing support and a first connecting plate; the first winding drum is used for winding the wire to be processed; the two transducer clamping plates are symmetrically arranged, fixed to the height-increasing support through bolts and clamp the outer wall of the ultrasonic transducer; the height-increasing support is fixed to the first connecting plate through bolts and provides mounting space for the first winding drum; the first connecting plate is provided with a second thread and a first pin hole and used for fixing the ultrasonic vibration mechanism to a universal interface of the base of the unidirectional stretching mechanism; and the base is located below the beam.

4. The apparatus for use in ultrasonic-assisted drawing of a micro-wire of nickel-titanium alloy according to claim 1, characterized in that, The drawing die is cylindrical, the first fastener is a fastening nut, the drawing die is fixed in the top-end cavity of the variable amplitude rod through the pre-tightening force generated by screwing the fastening nut and the first thread in the top end of the variable amplitude rod; the ultrasonic transducer makes the drawing die reciprocate in the first direction; and the ultrasonic transducer is provided with a circular through hole in the center and used for the wire to pass through. The frequency of the ultrasonic vibration output by the ultrasonic transducer is 38 kHz or 41 kHz.

5. The apparatus for use in ultrasonic-assisted drawing of a micro-wire of nickel-titanium alloy according to claim 1, characterized in that, The rigid connecting plate comprises a second pin hole and a third thread for fixing the centering drawing mechanism to the universal interface of the unidirectional stretching mechanism beam; the first platform is fixed to the rigid connecting plate through preset screw holes; the first platform is provided with a first guide rail extending in the second direction, and the intermediate platform is driven to adjust the position in the second direction along the first guide rail by rotating the first adjusting member; the intermediate platform is provided with a second guide rail extending in the third direction, and the second platform is driven to adjust the position in the third direction along the second guide rail by rotating the second adjusting member; the second platform is fixed to the winch assembly through preset screw holes.

6. The apparatus for use in ultrasonic-assisted drawing of a micro-wire of nickel-titanium alloy according to claim 1, characterized in that, The winch assembly comprises a rack, a stepping motor, a shaft coupling, a mandrel, a second winding drum and a bearing; the second winding drum is rigidly connected to the mandrel, one end of the mandrel is fixedly connected to the shaft coupling, and the other end is rotatably connected to the rack through the bearing; the second fastener is a fixed bolt, screw holes are provided on the winding drum, the wire is wound on the fixed bolt and screwed into the fixed bolt, and the pre-tightening force of the fixed bolt forms a stable clamping of the wire between the head of the fixed bolt and the outer wall of the second winding drum; the stepping motor is fixed to the rack through preset screw holes, and the torque output end of the stepping motor is rigidly connected to the shaft coupling for driving the mandrel and the second winding drum to rotate.

7. The apparatus for use in ultrasonic-assisted drawing of a microfilament of nickel-titanium alloy according to claim 6, characterized in that, The surface material of the second winding drum is rubber or metal.

8. The apparatus for use in ultrasonic-assisted drawing of a microfilament of nickel-titanium alloy according to claim 6, characterized in that, The wire collecting speed of the winch assembly is 1mm / s-300mm / s.

9. The apparatus for use in ultrasonic-assisted drawing of a micro-wire of nickel-titanium alloy according to claim 1, characterized in that, The mass of the centering drawing platform is less than or equal to 2.1kg.

10. A method of using ultrasonic assisted drawing of a nickel-titanium alloy micro wire, characterized by, The method uses the device for ultrasonic-assisted drawing of nickel-titanium alloy micro-wire according to any one of claims 1-9, and the method comprises the following steps: One end of the nickel-titanium alloy thick wire is passed through the drawing die and fixed to the winch assembly; The unidirectional stretching mechanism is started, the beam drives the centering drawing mechanism to move in the first direction, and the nickel-titanium alloy thick wire is drawn; the wire axis and the drawing die hole axis are accurately centered by observing the force sensor reading of the unidirectional stretching mechanism and finely adjusting the bidirectional fine adjustment assembly; During the drawing process, the ultrasonic transducer of the ultrasonic vibration mechanism is turned on; The change of drawing force before and after turning on the ultrasonic transducer is recorded and analyzed by the unidirectional stretching mechanism; wherein the drawing force decreases by 30%-50% after turning on the ultrasonic transducer.

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